Find preorder traversal of a binary tree from its inorder and postorder sequence
Write an efficient algorithm to find a binary tree’s preorder traversal from its inorder and postorder sequence without constructing the tree.
Tag: Hashing
Find all symmetric pairs in an array of pairs
Given an array of pairs of integers, find all symmetric pairs, i.e., pairs that mirror each other. For instance, pairs (x, y) and (y, x) are mirrors of each other.
Construct the longest palindrome by shuffling or deleting characters from a string
Write an efficient algorithm to construct the longest palindrome by shuffling or deleting characters from a given string.
Group elements of an array based on their first occurrence
Given an unsorted integer array containing many duplicate elements, rearrange it such that the same element appears together and the relative order of the first occurrence of each element remains unchanged.
Find the first non-repeating character in a string by doing only one traversal of it
Given a string, find the first non-repeating character in it by doing only one traversal of it.
Efficiently calculate the frequency of all elements present in a limited range array
Given an unsorted integer array whose elements lie in the range 0 to n-1 where n is the array size, calculate the frequency of all array elements in linear time and using constant space.
Find all common elements present in each row of a matrix
Given an M × N matrix, Function to find all common elements present in every row.
Replace each array element by its corresponding rank
Given an array of distinct integers, replace each array element by its corresponding rank in the array. The minimum array element has the rank 1; the second minimum element has a rank of 2, and so on…
Find the minimum index of a repeating element in an array
Given an integer array, find the minimum index of a repeating element in linear time and doing just one traversal of the array.
Find an index of the maximum occurring element with equal probability
Given an integer array, find the index of the maximum occurring element with an equal probability.
Check if an array is formed by consecutive integers
Given an integer array, check if only consecutive integers form the array.
Find two non-overlapping pairs having the same sum in an array
Given an unsorted integer array, find two non-overlapping pairs in it having the same sum.