Flatten Binary Tree to Linked List Given a binary tree, flatten it to a linked list in-place. For example, Given 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 tag: tree, […]
Longest Common Prefix Write a function to find the longest common prefix string amongst an array of strings. tag: string 好久没一遍AC了。 直接暴力搜就好。 遍历整个字符串数组，每次查看位于n位置的字符是否相等，如果有一个不等则返回，如果全相等则n++。 class Solution { public: string longestCommonPrefix(vector<string> &strs) { int n = 0; bool isFinish = false; if(strs.empty()){ return string(“”); } while(!isFinish){ char c; if(strs[0].size() == n){ isFinish […]
Roman to Integer Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. tag: math, string 9/28/2015 update class Solution { public: unordered_map<char, int> map; int romanToInt(string s) { map[‘I’] = 1; map[‘V’] = 5; map[‘X’] = 10; map[‘L’] […]
Integer to Roman Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. tag: string, math 9/28/2015 update class Solution { public: vector<string> roman = {“M”, “CM”, “D”, “CD”,”C”,”XC”,”L”,”XL” ,”X”,”IX”,”V”,”IV”,”I”}; vector<int> value = {1000, 900, 500, 400, 100, 90, […]
Container With Most Water Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a […]
String to Integer (atoi) Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases. Notes: It is intended for this problem to be specified vaguely […]
ZigZag Conversion The string “PAYPALISHIRING” is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility) P A H N A P L S I I G Y I R And then read […]
Add Two Numbers You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. Input: (2 -> 4 -> 3) + (5 -> 6 […]
Longest Substring Without Repeating Characters Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1. tags: hash table, […]
LRU Cache Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set. get(key) – Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1. set(key, value) – Set or […]
