- Sum of array elements
- Reverse an Array
- Maximum and Minimum Of Array Elements
- Sum Of Digits
- Pascal Triangle
- Alone in couple
- Sum of Array
- Odd or Even
- a^b (Set 1)-(ambiguous)
- Number of factors
- Palindrome String
- Armstrong Numbers
- Greatest of three numbers
- Swap two numbers
- Multiply 2 matrices
- Sum of Series
- Series AP
- Small Factorial
- Addition of Two Numbers
- Print Elements of Array
- Area of Rectange, Right Angled Triangle and Circle
- Binary number to decimal number
- Vowel or Not
- Print table
- Simple Interest
- Compound Interest
- Sum of Digit is Pallindrome or not
- Surface Area and Volume of Cuboid
- Automorphic Number
- Sum of an AP
- Sum of GP
- Print 1 to n without using loops
- nPr
- Remove Spaces
- Value equal to index value
- All divisors of a natural number
- Check if a number is Perfect Square
- Swap kth elements
- Second Largest
- Reverse digits
- Smaller and Larger
- Average
- Binary representation
- Check if an array is sorted
- 12 hour clock addition
- Cube root of a number
- Parallel or Perpendicular?
- Find the median
- Mean
- Number of divisors
- Sum of Digits Multiple - copy
- Perfect Number
- Multiply Array
- At least two greater elements
- Compete the skills
- Print the left element
- C++ Loops | Set 1 (Print a string N times)
- Distance between 2 points
- Sum of elements in a matrix
- Reversing the vowels
- Display longest name
- C++ Operators | Set 1 (Arithmetic)
- Reverse a String
- C++ Hello World
- C++ if-else (Decision Making)
- C++ Arrays (Sum of array) | Set 1
- C++ Strings
- C++ Array (print an element) | Set 2
- C++ Switch Case Statement
- C++ Operators (Relational) | Set 2
- Floyd's triangle
- GCD of two numbers
- Largest Element in Array
- C++ Data Types
- Count of smaller elements
- Split Strings
- Find Index
- Change the string
- Extract the integers
- Check if two given circles touch each other
- Sum of odd and even elements
- Sum of AP series
- Perfect Arrays
- Replace all 0's with 5
- Multiply Matrices
- Print alternate elements of an array

Name

Sahil Bansal

Institution

Rank in Institute

#3

Courses Attended

Campus Ambassador

Other Profile Link

Overall Coding Score: 1500

Monthly Coding Score: 0

Weekly Coding Score: 0

- Search an Element in an array
- Binary String
- Consecutive elements
- Factorial
- Prime Number
- LCM And GCD
- GCD of Array
- Repetitive Addition Of Digits
- Searching a number
- Power of 2
- Series GP
- Sort The Array
- Celsius to Fahrenheit Conversion
- Pythagorean Triplet
- Nth Fibonacci Number
- Sort a String
- Strong Number
- Print the Kth Digit
- Doubling the value
- Majority Element
- Sieve of Eratosthenes
- Shortest path from 1 to n
- Amend The Sentence
- Count possible triangles
- Rotate Array
- Permutations of a given string
- Parity of unsigned integer
- Check if the number is Fibonacci
- Missing number in array
- Rock Paper Scissors!
- Array of alternate +ve and -ve no.s
- Maximum product of two numbers
- Number of paths
- Numbers containing 0's from 1 to N
- Segregate Even and Odd numbers
- Count total set bits
- Number is sparse or not
- Bit Difference
- Count numbers containing 4
- Reverse sub array
- Odd Divisors
- Greater on right side
- Immediate Smaller Element
- Count zero
- Perfect Squares in a Range
- nth digit of Fibonacci
- Sum of distinct elements
- Binary Array Sorting
- Intersection of two arrays
- Union of two arrays
- Convert array into Zig-Zag fashion
- Remove character
- Perfect Cubes in a Range
- Number of occurrence
- Maximum repeating number
- Point lies or not
- k largest elements
- Student record
- Pairs of prime number
- Minimum difference pair
- Roots of Quadratic Equation
- Check if a number is power of another number
- Remove recurring digits
- Find position of set bit
- Sum of all prime numbers between 1 and N.
- Pattern Jumping
- Jumping Geek
- Sum of Digits Divisibility
- Maximum distance
- Maximum money
- Palindromic Subsequences
- Absolute distinct count
- Generate Binary Numbers
- Shortest direction
- Factorial Number
- Count the numbers
- Find the Odd Occurence
- Find the remainder
- Angle between hour and minute hand
- Keypad typing
- Maximum Possible Sum of Products
- Rotating an Array
- Total distance travelled in an array
- Sum of Products
- LCM of given array elements
- Number of Integer solutions
- Searching an element in a sorted array
- Total count
- Surpasser Count
- The Lazy Caterer's Problem
- Matching Pair
- Sum of primes
- Merge and Sort
- Composite Series
- Rotate by 90 degree
- Reverse array in groups
- The AND Gate
- The OR Gate
- 1's Complement
- The XOR Gate
- Good String
- Set Bits
- Repeated sum of digits
- Subset Sums
- Professor and Parties
- Longest Consecutive 1's
- Sum of divisors
- Common Divisors
- Count Squares
- Sum of Consecutives
- Disarium Number
- Pairs with given XOR
- No of Carry Operations
- Elements before which no element is bigger
- Minimize the sum of product
- Missing number
- Make a Distinct Digit Array
- Reverse each word in a given string
- Permutations in array
- String with numbers at its end
- Replace the Bit
- Form a Triangle
- Squares in a Matrix
- Check squares
- Find duplicates under given constraints
- Find first and last occurrence of x
- Type of array
- Ladoo problem
- Sum of dependencies in a graph
- Stuffs Division
- Sort in specific order
- Check if two arrays are equal or not
- Form largest number from digits
- Sherlock a Detective
- Check if string is rotated by two places
- Check if divisible by 11
- Unique Numbers
- XOR of all elements
- Check if divisible by 4
- Learning Output
- Substrings with similar first and last characters
- India's unique railway track
- Check if divisible by 36
- Find first set bit
- Minimize sum of alternate product
- Check for subsequence
- Check if the door is open or closed
- Find first repeated character
- Count even substrings
- Tidy Number
- Check if date is valid
- Magical Number
- Geek and Coffee Shop
- A guy with a mental problem
- Fake Profile
- Check if divisible by 5
- Wrong Ball
- Magical String[Duplicate Problem]
- Index of first 1 in a sorted array of 0’s and 1’s
- Strong Numbers
- Sherlock and his Enemies
- Does array represent Heap
- Missing number in shuffled array
- Find the element that appears once in sorted array
- Thief trying to escape
- Last index of One
- Arranging the array
- Cyclically rotate an array by one
- Print an array in Pendulum Arrangement
- Transpose of Matrix
- First element to occur k times
- Check whether K-th bit is set or not
- Length of Last word
- Extract Maximum
- Uncommon characters
- Find the smallest and second smallest element in an array
- Find minimum and maximum element in an array
- Find second largest element
- URLify a given string
- Reverse a string with spaces intact
- Rotate Bits
- Find Smallest Missing in Sorted
- Minimum move to front operations
- Smallest power of 2 greater than or equal to n
- Area of a triangle
- Pair array product sum
- Pair cube count
- Evaluate the expression
- All numbers with specific difference
- Count pair sum
- First Come First Serve
- K-th distinct element
- Friendly Array
- Balanced Array
- Swap and Maximize
- Max Sum Subarray of size K
- Minimum Difference among K
- Check if a string is Isogram or not
- Longest Equal Prefix
- Krishnamurthy number
- Check Arithmetic Progression
- Sort the Half Sorted
- Alternative Sorting
- Rightmost different bit
- Max value after m range operation
- Check set bits
- Set kth bit
- Fighting the darkness
- Sorting Employees
- Count Pairs Odd Xor
- Difficulty of sentence
- Toggle bits given range
- Twice counter
- Shuffle integers
- Elements in the Range
- Min value of x
- First K natural numbers
- Print first n Fibonacci Numbers
- Remove repeated digits in a given number
- Sum of distinct elements for a limited range
- Count triplets with sum smaller than X
- Odd to Even
- Minimum number of flipped bits
- Total number of Strings
- Minimum Distinct Ids
- Find the Highest number
- Product Sum
- Print Matrix in snake Pattern
- Minimum number to form the sum even
- Anagram Palindrome
- Closest Number
- Pronic Number
- Transform to prime
- First and last occurrences of X
- Positive and negative elements
- Boolean String Value
- Finger Game
- Smallest number repeating K times
- Part Sort
- Anshuman's Favourite Number
- Absolute Difference of 1
- Remove common characters and concatenate
- Shortest un-ordered subarray
- Repeated I.Ds
- Left Rotate Matrix K times
- Rectangle Number
- Sum of Digit Modified
- Count the characters
- Find k-th character in string
- Good or Bad string
- Repeated Character
- Merge two strings
- Sort String
- Maximize OR
- Difference between highest and lowest occurrence
- Find unique element
- Sum of first n terms
- Generate all cyclic permutations of a number
- G.F Series
- Find the fine
- Minimum Product of k Integers
- Maximize ∑arr[i]*i of an Array
- Sort the string in descending order
- Find N-th term in the series
- Sum of all subsets formed by first N natural numbers
- Count number of elements between two given elements in array
- Remove all characters other than alphabets
- Sandwiched_Vowels
- Narcissistic number
- Last index of a character in the string
- Distinct Elements in a Stream
- Break the digital root code
- Check if the number is balanced
- Count the characters in each word in a given sentence
- Find sum of even factors of a number
- The problem of identical arrays
- Remove consonants from a string
- Product of maximum in first array and minimum in second
- Most frequent word in an array of strings
- Encoding names
- Crazy String
- Set all odd bits
- Message Spreading
- Convert the string
- Last duplicate element in a sorted array
- Sum of f(a[i], a[j]) over all pairs in an array of n integers
- Game with nos
- Ishaan Loves Chocolates
- The Penalty Shootout
- How Many X's?
- Prime String
- Height of Heap
- Fibonacci to N
- Average Count Array
- Geek and the equation
- Print Linked List elements
- Count nodes of linked list
- Node at a given index in linked list
- Power of Four
- Size of Binary Tree
- Inorder Traversal
- Bubble Sort
- Count Leaves in Binary Tree
- Selection Sort
- Height of Binary Tree
- Finding middle element in a linked list
- Postorder Traversal
- Implement stack using array
- Implement Queue using array
- Square root
- Binary Search
- Remove duplicate elements from sorted Array
- Add two fractions
- Replace all 0's with 5
- Preorder Traversal
- Implement strstr
- C++ STL | Set 1 (vector)
- C++ STL | Set 4 (stack)
- C++ STL | Set 5 (queue)
- Search a node in BST
- Implement Atoi
- Find triplets with zero sum
- Minimum element in BST
- Anagram of String
- Linked List Length Even or Odd?
- Delete Alternate Nodes
- Identical Linked Lists
- Find the Sum of Last N nodes of the Linked List
- Modular Node
- Find n/k th node in Linked list
- Maximum in Struct Array
- Queue Reversal
- Triplet Family
- Sum of Binary Tree
- Insert in Middle of Linked List
- longest substring containing '1'
- Pairwise Consecutive Elements
- Count Non-Leaf Nodes in Tree
- Product of array elements

- Frequencies of Limited Range Array Elements
- Anagram
- Adding One
- Wave Array
- Maximum Gap
- Pattern Searching
- Print Pattern
- Rotation
- Search in a Rotated Array
- Rectangles in N*N Board
- Squares in N*N Chessboard
- Palindrome numbers
- Magic Number
- Maximize Toys
- Large Factorial
- Trailing zeroes in factorial
- Maximize Number of 1's
- Non Repeating Character
- a^b(Set 2)
- Sum of Middle Elements of two sorted arrays
- Good Pairs
- First Repeating Element
- Count Occurences of Anagrams
- Reverse words in a given string
- Count Substrings
- Check if a given string is a rotation of a palindrome
- Move all zeroes to end of array
- Remove all duplicates from a given string
- Activity Selection
- Spirally traversing a matrix
- Sort an array of 0s, 1s and 2s
- Two numbers with sum closest to zero
- Finding Number
- Maximum value in a bitonic array
- Next greater number set digits
- Finding Position
- Single Number
- Segregate even and odd nodes in a Linked List
- Count increasing Subarrays
- Element that appears once where every element occurs twice
- Longest Distinct characters in string
- Replace by X
- Column name from a given column number
- Maximum Product Subarray
- N meetings in one room
- Remove Duplicates
- Kth distance
- Addition of submatrix
- Maximum sum increasing subsequence
- Array to BST
- Sum of two numbers represented as arrays
- Facing the sun
- Max Sum without Adjacents
- Key Pair
- Maximum Difference
- Add Binary Strings
- Product array puzzle
- Reverse Bits
- Count Smaller elements
- Reach the Nth point
- Subarray with given sum
- Adjacents are not allowed
- Count numbers
- Leaders in an array
- Count number of hops
- Equal to product
- Count pairs with given sum
- Inorder Traversal and BST
- Segregate 0s and 1s
- Triplet Sum in Array
- Two Repeated Elements
- Three Great Candidates
- Overlapping rectangles
- Minimum element in a sorted and rotated array
- Search in a matrix
- Number Of Open Doors
- K-Pangrams
- Generate binary string
- Count the Zeros
- Distinct absolute array elements
- 0 - 1 Knapsack Problem
- Pangram Strings
- Valid Substring
- Count the Reversals
- Special array reversal
- Number that are not divisible
- Game of Death in a circle
- Left out candies
- Perfect Numbers
- Product of two digit numbers
- Permutation with Spaces
- Element appearing once
- Equilibrium point
- Floor in a Sorted Array
- Buildings receiving sunlight
- RegEx matching
- Max value
- Finding the numbers
- Prime Factors
- Least Prime Factor
- Left or Right Positioned Array
- Maximize sum after K negations
- Adding Ones
- Equal Point in Sorted Array
- Largest Even Number
- Count Pairs in an Array
- Sum of elements between k1'th and k2'th smallest elements
- Min sum formed by digits
- Move all negative elements to end
- String Manipulation
- Chocolate Distribution Problem
- 1[0]1 Pattern Count
- Knapsack with Duplicate Items
- Find sum of divisors
- Flood fill Algorithm
- Pair with greatest product in array
- Maximum no of 1's row
- Drive the car
- Next Greater Even Number
- Smallest subarray with sum greater than x
- Rahul a Geek
- Game of XOR
- Minimum Operations
- Equal point in a string of brackets
- Find all pairs with a given sum
- Meta Strings
- Excel Sheet | Part - 2
- Longest Palindromic Subsequence
- Fractional Knapsack
- K-th element of two sorted Arrays
- Evaluation of Postfix Expression
- Maximum difference Indexes
- Common elements
- Rod Cutting
- Fill array with 1's
- Element with left side smaller and right side greater
- Transitive closure of a Graph
- Array Subset of another array
- Sum of product of all pairs
- Four Elements
- Paths to reach origin
- Group Anagrams Together
- Find the closest prime number to a given number
- Sum equals to Sum
- Find Pair Given Difference
- Carry counter
- Count the elements
- Second most repeated string in a sequence
- Count all possible paths from top left to bottom right
- k modulus array element
- Sort the given array after applying the given equation
- Assign Mice Holes
- Mr Modulo and Pairs
- Rearrange a string
- Minimum Number in a sorted rotated array
- Sort by Absolute Difference
- Number of Groups
- Toppers Of Class
- String Ignorance
- Count the number of ways to tile the floor of size n x m using 1 x m size tiles
- Bitonic Generator Sort
- Nth item through sum
- Minimum indexed character
- Consecutive Array Elements
- Stickler Thief
- Minimum Swaps for Bracket Balancing
- Even and odd elements at even and odd positions
- Find the most frequent digit
- Compute (a*b)%c
- Maximum number of zeroes
- Merging two unsorted arrays in sorted order
- Transform the array
- Roll the characters of a String
- Chocolate Station
- Boundary Elements of Matrix
- Count the triplets
- Star elements
- Three consecutive duplicates
- Sum of two large numbers
- Find the minimum time
- Prime number of set bits
- Remove minimum number of elements
- Pairs with Positive Negative values
- Numbers containing 1, 2 and 3
- Non-Repeating Element
- Pairs which are Divisible by 4
- Maximum AND Value
- Find winner of the Game of Nim
- Maximum distinct elements after removing K elements
- Check if array contains contiguous integers with duplicates allowed
- Maximum height of the staircase
- Winner of an election
- Ease the Array
- Numbers with prime frequencies greater than or equal to k
- Counts Zeros Xor Pairs
- Easy string
- C++ Matrix Rotation by 180 degree
- Check if a number is divisible by 8
- Ishaan and Sticks
- Find the closest pair from two arrays
- Common Divisor
- The Non-repetitive String
- Print Bracket Number
- Minimum changes to make all substrings distinct
- Smallest greater elements in whole array
- Save Ironman
- Are you "Perfect"
- Sahil loves gfg
- Sahil love good scorer
- Smriti's String
- Special path
- Print adjacency list
- SP - Palindrome Family
- Geeks and the test
- Geek and the base
- SP - Stack Design
- Reverse a linked list
- Occurence of an integer in a Linked List
- Delete N nodes after M nodes of a linked list
- Pairwise swap elements of a linked list
- Given a linked list of 0s, 1s and 2s, sort it.
- Add two numbers represented by linked lists
- Add 1 to a number represented as linked list
- linked list of strings forms a palindrome
- Merge 2 sorted linked list in reverse order
- Linked List in Zig-Zag fashion
- Detect Loop in linked list
- Remove duplicates from an unsorted linked list
- Merge Sort
- Quick Sort
- Right View of Binary Tree
- K distance from root
- Mirror Tree
- Two Mirror Trees
- Maximum Width of Tree
- Diameter of Binary Tree
- Check for Balanced Tree
- Nth node from end of linked list
- Left View of Binary Tree
- Delete Middle of Linked List
- Merge two sorted linked lists
- Sum Tree
- Decimal Equivalent of Binary Linked List
- Transform to Sum Tree
- Queue using two Stacks
- Remove duplicate element from sorted Linked List
- Stack using two queues
- Level order traversal in spiral form
- Reverse Level Order Traversal
- DFS of Graph
- Insert a node in a BST
- BFS of graph
- Lowest Common Ancestor in a Binary Tree
- Determine if Two Trees are Identical
- Root to leaf path sum
- Print all nodes that don't have sibling
- Postorder traversal from given Inorder and Preorder traversals
- Absolute List Sorting
- Lowest Common Ancestor in a BST
- Implement two stacks in an array
- Run Length Encoding
- Level order traversal Line by Line
- Print BST elements in given range
- Largest subarray with 0 sum
- Minimum Depth of a Binary Tree
- Odd even level difference
- Binary Tree to BST
- Equilibrium index of an array
- Unique rows in boolean matrix
- Remove every k'th node
- Is Binary Tree Heap
- Validate an IP Address
- Multiply two linked lists
- Josephus problem
- Expression Tree
- Check if Linked List is Palindrome
- Find perimeter of shapes
- Delete a Node in Single Linked List
- Kth largest element in BST
- Count distinct elements in every window
- Max Level Sum in Binary Tree
- Sort a stack
- Print Common Nodes in BST
- Level order traversal
- Peak element
- Inorder Successor in BST
- Delete nodes greater than k
- Index Of an Extra Element
- Union of Two Linked Lists
- Intersection of Two Linked Lists
- Insert in a Sorted List
- Ancestors in Binary Tree
- Level of a Node in Binary Tree
- Sum of leaf nodes in BST
- Root to Leaf Paths
- Maximum path sum
- Max and min element in Binary Tree
- Counting elements in two arrays
- Reverse a string using Stack
- Modify Linked List-1
- Triplet with 0 sum in BST
- Symmetric Tree
- Construct Tree from Inorder & Preorder
- Vertical sum
- Count Pairs whose sum is equal to X
- Check if Tree is Isomorphic
- Diagonal Sum In Binary Tree
- Find length of Loop
- Median of BST
- Reverse First K elements of Queue
- Height of Spiral Tree
- Sum of Leaf Nodes
- Sum of Right Leaf Nodes
- Sum of Left Leaf Nodes
- Closest Neighbor in BST
- Check if two Nodes are Cousins
- ZigZag Tree Traversal
- Sum of Leaf Nodes at Min Level
- Tilt of Binary Tree
- Delete middle element of a stack
- Vertical Width of a Binary Tree

- Coin Change
- Kadane's Algorithm
- Find Missing And Repeating
- Excel Sheet | Part - 1
- Overlapping Intervals
- Maximum Index
- Next Permutation
- Longest Increasing Subsequence
- Parenthesis Checker
- Longest Common Subsequence
- Minimum number of jumps
- Count ways to reach the n'th stair
- Count ways to N'th Stair(Order does not matter)
- Count of n digit numbers whose sum of digits equals to given sum
- Edit Distance
- nCr
- Maximum Rectangular Area in a Histogram
- Consecutive 1's not allowed
- Path in Matrix
- Trapping Rain Water
- Case-specific Sorting of Strings
- Factorials of large numbers
- Find Prime numbers in a range
- Largest Number formed from an Array
- Jumping Numbers
- Longest Palindrome in a String
- Rearrange Array Alternately
- Relative Sorting
- Maximum of all subarrays of size k
- Largest square formed in a matrix
- Row with max 1s
- Boolean Matrix Problem
- Sorting Elements of an Array by Frequency
- Design a tiny URL or URL shortener
- Nuts and Bolts Problem
- Rotate a 2D array without using extra space
- Number of ways
- Minimum Cost of ropes
- Sum of Query II
- Form a palindrome
- Inversion of array
- Maximum length Bitonic Subarray
- Smallest number on left
- Longest consecutive subsequence
- Stock span problem
- Convert an array to reduced form
- Number to words
- Palindromic Array
- Is Binary Number Multiple of 3
- Possible groups
- Bleak Numbers
- Minimum sum
- Digit multiplier
- Largest number in K swaps
- Minimize the heights
- Next larger element
- X Total Shapes
- Total Decoding Messages
- Unique BST's
- Matchsticks game
- Combination Sum
- Combination Sum - Part 2
- Kth smallest element
- Transform String
- Longest Common Substring
- Rotate and delete
- Recursively remove all adjacent duplicates
- Trie | (Insert and Search)
- Replace O's with X's
- Find all four sum numbers
- Max absolute difference
- Unit Area of largest region of 1's
- First non-repeating character in a stream
- Count subsequences of type a^i b^j c^k
- Stepping Numbers
- Zero Sum Subarrays
- Magnet Array Problem
- Smallest distinct window
- Floyd Warshall
- Infix to Postfix
- Smallest Positive missing number
- Longest Bitonic subsequence
- Maximum Intervals Overlap
- Job Sequencing Problem
- Longest Common Prefix in an Array
- In First But Second
- Row with minimum number of 1's
- Matrix Chain Multiplication
- Find the Maximum sum
- The Painter's Partition Problem
- Shivani hates Consecutive numbers
- SP - Special Subsequences
- Reverse a Linked List in groups of given size.
- Count BST nodes that lie in a given range
- Check for BST
- Tree from Postorder and Inorder
- Bottom View of Binary Tree
- Delete without head pointer
- Intersection Point in Y Shapped Linked Lists
- Add all greater values to every node in a BST
- Construct Binary Tree from Parent Array
- Connect Nodes at Same Level
- Clone a linked list with next and random pointer
- Flattening a Linked List
- Diagonal Traversal of Binary Tree
- Boundary Traversal of binary tree
- Delete a node from BST
- Detect cycle in a directed graph
- Min distance between two given nodes of a Binary Tree
- Maximum difference between node and its ancestor
- The Celebrity Problem
- Print a Binary Tree in Vertical Order
- Merge K sorted linked lists
- Find the number of islands
- Get minimum element from stack
- Serialize and Deserialize a Binary Tree
- Circular tour
- Wildcard Pattern Matching
- Max rectangle
- Make Binary Tree From Linked List
- Generate IP Addresses
- Check if subtree
- Remove loop in Linked List
- Max length chain
- Largest BST
- Interleaved Strings
- Find the Closest Element in BST
- Delete keys in a Linked list
- Merge two BST 's
- Print Nodes having K leaves
- Top View of Binary Tree
- k-th smallest element in BST
- Polynomial Addition
- Find a pair with given target in BST
- K-Sum Paths
- Foldable Binary Tree
- Leftmost and rightmost nodes of binary tree
- Construct tree from Inorder and LevelOrder
- Pairs violating BST property
- Count Number of SubTrees having given Sum
- C++ Generic sort

- Maximum of minimum for every window size
- Merge Without Extra Space
- Allocate minimum number of pages
- A Simple Fraction
- Ugly Numbers
- Longest valid Parentheses
- Solve the Sudoku
- Find median in a stream
- Count the subarrays having product less than k
- Reorder List
- Binary Tree to DLL
- Nodes at given distance in binary tree
- Fixing Two nodes of a BST