Count decodings of a given sequence of digits
Given a positive number, map its digits to the corresponding alphabet in the mapping table, and return the count of the total number of decodings possible.
Tag: Medium
Determine whether an array can be divided into pairs with a sum divisible by `k`
Given an integer array, determine if it can be divided into pairs such that the sum of elements in each pair is divisible by a given integer k.
Perform boundary traversal on a binary tree
Given a binary tree, perform the boundary traversal of it. The solution should print the boundary nodes starting from the root of the tree, in an anti-clockwise direction, without any duplicates.
Find the previous smaller element for each array element
Given an integer array, find the previous smaller element for every array element. The previous smaller element of a number x is the first smaller number to the left of x in the array.
Return k’th largest element in a stream
Given an infinite stream of integers, return the element representing the k’th largest element in the stream.
Fix children-sum property in a binary tree
Write an efficient algorithm to fix the children-sum property in a given binary tree. The only operation allowed is an increment operation on the node’s value.
Find the shortest unique prefix for every word in an array
Given an array of words where no word is the prefix of another, find the shortest unique prefix to identify each word in the array uniquely.
Extract leaves of a binary tree into a doubly-linked list
Given a binary tree, extract all its leaves into a doubly-linked list, i.e., remove all leaf nodes from the binary tree and construct a doubly linked list out of them.
Find a pair with the given sum in a circularly sorted array
Given a circularly sorted integer array, find a pair with a given sum. Assume there are no duplicates in the array, and the rotation is in an anti-clockwise direction around an unknown pivot.
Find the intersection point of two linked lists
Given two linked lists, where the tail of the second list points to a node in the first list, find the node where both lists intersect.
Find all substrings containing exactly `k` distinct characters
Given a string and a positive integer k, find all distinct substrings of any length containing exactly k distinct characters.
Find the next greater element for every array element
Given an integer array, find the next greater element for every array element. The next greater element of a number x is the first greater number to the right of x in the array.