题目: Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following unique permutations: [ [1,1,2], [1,2,1], [2,1,1] ] 题解: Solution 1 (TLE) class Solution { public: void dfs…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 方法一:递归 方法二:回溯法 日期 题目地址:https://leetcode.com/problems/permutations-ii/description/ 题目描述 Given a collection of numbers that might contain duplicates, return all possible unique p…

Permutations II Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following unique permutations:[1,1,2], [1,2,1], and [2,1,1]. 首先分析一下与Permutations有何差异. 记当前位置为start,当前排列数…

一天一道LeetCode系列 (一)题目 Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [1,1,2], [1,2,1], and [2,1,1]. (二)解题 求全排列数.具体思路可以参考[一天一道LeetCode]#…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 递归 回溯法 日期 题目地址:https://leetcode.com/problems/subsets-ii/description/ 题目描述 Given a collection of integers that might contain duplicates, nums, return all possible subsets (the po…

[Description] 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 target,…

[问题]实现一个基本的计算器来计算一个简单的字符串表达式的值.字符串表达式仅包含非负整数,+, - ,*,/ 四种运算符和空格  .整数除法仅保留整数部分. 输入: "3+2*2" 输出: 示例 : 输入: " 3/2 " 输出: [思路] 总体思路来说,我们遍历字符串的每个字符,注意:加减乘除以及空格的ASCII码 < '0'.如果这个字符为数字字符,需要将两个非数字字符之间的不包含空格的字符串变换成数值!表达式:num = num * 10 - '0' +…

[问题]n 皇后问题研究的是如何将 n 个皇后放置在 n×n 的棋盘上,并且使皇后彼此之间不能相互攻击. 上图为 8 皇后问题的一种解法.给定一个整数 n,返回 n 皇后不同的解决方案的数量. 示例: 输入: 输出: 解释: 皇后问题存在如下两个不同的解法. [ [".Q..", // 解法 1 "…Q", "Q…", "..Q."], ["..Q.", // 解法 2 "Q…", &q…

[问题]给定一个非负整数数组,你最初位于数组的第一个位置.数组中的每个元素代表你在该位置可以跳跃的最大长度.你的目标是使用最少的跳跃次数到达数组的最后一个位置. 示例: 输入: [,,,,] 输出: 解释: 跳到最后一个位置的最小跳跃数是 . 从下标为 跳到下标为 的位置,跳 步,然后跳 步到达数组的最后一个位置. 说明: 假设你总是可以到达数组的最后一个位置 [思路]由于题目中规定总能到达数组的最后一个位置,因此我们在遍历数组时每次都要去找最大的跳跃位置,只有到达了这个最远的边界end,我们才…

[题意] 输出N皇后问题的解法个数. [题解] 解法一:传统dfs回溯,模拟Q放置的位置即可,应该不难,虽然能通过,但是时间复杂度很高. 解法二:位运算大法好! 首先要明白这道题里两个核心的位运算 1.x & -x 代表除最后一位 1 保留,其它位全部为 0(这个是不是很熟悉,就是树状数组的lowbit哦) 这里要明白计算机存储数的时候存储的是补码,假设x为0101000,正数的补码还是正数,-x为1101000,其补码为1011000,然后0101000 & 1011000,就是保留x的…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 目录 题目描述 解题方法 方法一:库函数 方法二:递归 方法三:回溯法 日期 题目地址:https://leetcode.com/problems/permutations/description/ 题目描述 Given a collection of distinct numbers, return all possible permutations. For example, [1,…

Subsets II Given a collection of integers that might contain duplicates, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If S = [1,2,2], a so…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 全排列函数 回溯法 日期 题目地址:https://leetcode.com/problems/n-queens-ii/description/ 题目描述 The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queen…

  Word Ladder II 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, G…

Word Break II Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences. For example, givens = "catsanddog",dict = ["cat", &q…

Spiral Matrix II Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example,Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]   与Spiral Matrix类似:   class So…

Unique Paths II Total Accepted: 22828 Total Submissions: 81414My Submissions Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 an…

Path Sum II Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2], [5,8,4,5] ]     采用深度…

Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. For example, given s = "aab",Return 1 since the palindrome partitioning ["aa",…

Palindrome Partitioning II Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. For example, given s = "aab",Return 1 since the palindrome pa…

Combination Sum II Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. Each number in C may only be used once in the combination. Note: All numbers (including t…

Given an array of integers, every element appears three times except for one. Find that single one. Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory? 思路: 这个题是Single Number的进阶版,如果其他的数都出现两次而…

Permutations Given a collection of numbers, return all possible permutations. For example,[1,2,3] have the following permutations:[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1]. 解法一:递归 class Solution { public: vector<vector<int> > pe…

N-Queens II Follow up for N-Queens problem. Now, instead outputting board configurations, return the total number of distinct solutions. 简单的回溯法. cur[i] == j 代表第i行的皇后位于第j列. 对于每一行,尝试所有列, 如果当前行尝试的位置不与前面所有行的位置冲突,则可以递归到下一行. class Solution { public: int to…

题目: Given a collection of distinct numbers, return all possible permutations. For example,[1,2,3] have the following permutations: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ] 题解: 之前解过Next Permutation,故这个题可以重复调用nextPermutation函数产生全排列 Solu…

这道题是LeetCode里的第40道题. 题目要求: 给定一个数组 candidates 和一个目标数 target ,找出 candidates 中所有可以使数字和为 target 的组合. candidates 中的每个数字在每个组合中只能使用一次. 说明: 所有数字(包括目标数)都是正整数. 解集不能包含重复的组合. 示例 1: 输入: candidates = [10,1,2,7,6,1,5], target = 8, 所求解集为: [ [1, 7], [1, 2, 5], [2, 6]…

Subsets II Given a collection of integers that might contain duplicates, nums, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If nums = [1,2,2]…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址: https://leetcode.com/problems/h-index-ii/description/ 题目描述: Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a functio…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 字典 日期 题目地址:https://leetcode.com/problems/4sum-ii/description/ 题目描述 Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i]…

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example,Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] 思路: 我是直接套用了Spiral Matrix 的代码 class Solution { p…