Implement Queue using Stacks Implement the following operations of a queue using stacks. push(x) — Push element x to the back of queue. pop() — Removes the element from in front of queue. peek() — Get the front element. empty() — Return whether the queue is empty. Notes: You must […]

Kth Largest Element in an Array Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element. For example, Given [3,2,1,5,6,4] and k = 2, return 5. Note: You may assume k is always valid, […]

Flatten Binary Tree to Linked List Flatten a binary tree to a fake “linked list” in pre-order traversal. Here we use the right pointer in TreeNode as the nextpointer in ListNode. Have you met this question in a real interview? Yes Example 1 \ 1 2 / \ \ 2 […]

Longest Increasing Continuous subsequence II Give you an integer matrix (with row size n, column size m)，find the longest increasing continuous subsequence in this matrix. (The definition of the longest increasing continuous subsequence here can start at any row or column and go up/down/right/left any direction). Have you met this […]

One Edit Distance Given two strings S and T, determine if they are both one edit distance apart. two pointers. class Solution { public: bool isOneEditDistance(string s, string t) { int ls = s.size(); int lt = t.size(); if(abs(ls – lt) > 1) return false; int i = 0, j […]

Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. For example: Given n = 13, Return 6, because digit 1 occurred in the following numbers: 1, 10, 11, 12, 13. Brute force solution o(n) in time, TLE. […]

Palindrome Linked List Given a singly linked list, determine if it is a palindrome. Follow up: Could you do it in O(n) time and O(1) space? O(n) time, O(n)space solution, use a stack. /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * […]

Delete Node in a Linked List Write a function to delete a node (except the tail) in a singly linked list, given only access to that node. Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with value 3, the […]

Read N Characters Given Read4 The API: int read4(char *buf) reads 4 characters at a time from a file. The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the file. By using the read4 API, implement […]

Product of Array Except Self Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Solve it without division and in O(n). For example, given [1,2,3,4], return [24,12,8,6]. Follow […]