Sort List Sort a linked list in O(n log n) time using constant space complexity. tag: list, sort 9/22/2015 update a cleaner solution /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class […]
3Sum Closest Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution. For example, given array S = {-1 […]
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 […]
