454. 4Sum II 题意:给四个数组,每个数组内取一个数使得四个数和为0,问有多少种取法 思路:枚举为On4,考虑两个数组,On2枚举所有可能的和,将和的出现次数存入map中,On2枚举另两个数组,看是否加和为0 class Solution { public: int fourSumCount(vector<int>& A, vector<int>& B, vector<int>& C, vector<int>& D)…
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 line by line: "PAHNAPLSII…
Given a non-empty string containing an out-of-order English representation of digits 0-9, output the digits in ascending order. Note: Input contains only lowercase English letters. Input is guaranteed to be valid and can be transformed to its origina…
Given a 2D grid, each cell is either a wall 'W', an enemy 'E' or empty '0' (the number zero), return the maximum enemies you can kill using one bomb. The bomb kills all the enemies in the same row and column from the planted point until it hits the w…
You have a number of envelopes with widths and heights given as a pair of integers (w, h). One envelope can fit into another if and only if both the width and height of one envelope is greater than the width and height of the other envelope. What is…
A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Write a function to count the total strobogrammatic numbers that exist in the range of low <= num <= high. For example,Given low = "50&qu…
Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that: Only one letter can be changed at a time Each intermediate word must exist in the dictionary For example, Given: start = "hi…
You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters. For example, giv…
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 spe…
82. Remove Duplicates from Sorted List II https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/ 下面代码是自写hashmap版,练一下hashmap,用一般的map<int,int>红黑树map也能过. /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *…
August 7, 2015 周日玩这个算法, 看到Javascript Array模拟Deque, 非常喜欢, 想用C#数组也模拟; 看有什么新的经历. 试了四五种方法, 花时间研究C# SortedList class. Try to get some workout on the C# programming practice. 我的体会是代码写得太少, 要多读不同的代码, 多调试, 开阔对一个问题思考的思路和深度, 准确度, 实现能力. 1. Blog to read: http://…
一般用dfs来做 最简单的一种: 17. Letter Combinations of a Phone Number Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telephone buttons) is given below. Input:Digit s…
463. Island Perimeterhttps://leetcode.com/problems/island-perimeter/就是逐一遍历所有的cell,用分离的cell总的的边数减去重叠的边的数目即可.在查找重叠的边的数目的时候有一点小技巧,就是沿着其中两个方向就好,这种题目都有类似的规律,就是可以沿着上三角或者下三角形的方向来做.一刷一次ac,但是还没开始注意codestyle的问题,需要再刷一遍. class Solution { public: int islandPerime…
If you understand the comments below, never will you make mistakes with binary search! thanks to A simple CPP solution with lower_bound and C++ O(logn) Binary Search that handles duplicate, thanks to phu1ku 's answer on the second post. http://en.cpp…
原题链接在这里:https://leetcode.com/problems/alien-dictionary/ 题目: There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of words from the dictionary, wherewords are sorted lexic…
examination questions Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat…
https://leetcode.com/submissions/detail/32662938/ Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between t…
博客搬至blog.csgrandeur.com,cnblogs不再更新. 新的题解会更新在新博客:http://blog.csgrandeur.com/2014/01/15/LeetCode-OJ-Solution/ ———————————————————————————————————————— ———————————————————————————————————————— LeetCode OJ 题解 LeetCode OJ is a platform for preparing tech…
Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. 方法: Manacher's algorithm,具体看这里http://leetcode.com/2011/11/longest-palindrom…
原题链接在这里:https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/ 题目: Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor…
Problem Link: http://oj.leetcode.com/problems/word-ladder-ii/ Basically, this problem is same to Word Ladder I, which uses a double-direction BFS. However, the difference is that we need to keep track of all paths during the double-direction BFS in o…
Problem Link: http://oj.leetcode.com/problems/word-ladder/ Two typical techniques are inspected in this problem: Hash Table. One hash set is the words dictionary where we can check if a word is in the dictionary in O(1) time. The other hash set is us…
一. 题目 1. Two Sum II Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the ta…
一. 题目 1. Two SumTotal Accepted: 241484 Total Submissions: 1005339 Difficulty: Easy Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input would have exactly one solutio…
https://leetcode.com/problems/russian-doll-envelopes/ You have a number of envelopes with widths and heights given as a pair of integers (w, h). One envelope can fit into another if and only if both the width and height of one envelope is greater tha…
原题链接:http://oj.leetcode.com/problems/evaluate-reverse-polish-notation/ 题目描述: Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some example…
https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/ Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined…
