Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. Example: Given array nums =…

LeetCode 15 3Sum [sort] <c++> 给出一个一维数组,找出其中所有和为零的三元组(元素集相同的视作同一个三元组)的集合. C++ 先自己写了一发,虽然过了,但跑了308 ms... 我的做法是先排序,扫一遍,处理出unorder_map<0-a[i],i>的hash表.再\(O(n^2)\)枚举前两个元素,查表直接知道第三个元素的位置,然后将三元组加入到答案集合中,通过枚举时添加的限制条件规避重复元素. 复杂度\(O(n^2)\),由于使用了hash表,常数…

题目: 1. Two Sum 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 solution, and you may not use the same element twice. Given nums = [2, 7, 1…

1.two sum 用hash来存储数值和对应的位置索引,通过target-当前值来获得需要的值,然后再hash中寻找 错误代码1: Input:[3,2,4]6Output:[0,0]Expected:[1,2] 同一个数字不能重复使用,但这个代码没排除这个问题 class Solution { public: vector<int> twoSum(vector<int>& nums, int target) { vector<int> result; uno…

传送门 15. 3Sum My Submissions Question Total Accepted: 108534 Total Submissions: 584814 Difficulty: Medium Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the su…

15 3sum Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. Example: Given array…

一.题目说明 题目非常简洁15. 3Sum,读懂题目后,理解不难. 但 实话说,我们提交代码后,Time Limit Exceeded,最主要的是给了非常长的测试用例,我本地运行后87秒,确实时间非常长. 二.我的解答及问题 下面是我的解答代码,通过该例子可以学习如何写测试代码: #include<iostream> #include<vector> #include<unordered_map> #include<algorithm> using name…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The solut…

n数求和,固定n-2个数,最后两个数在连续区间内一左一右根据当前求和与目标值比较移动,如果sum<target,移动较小数,否则,移动较大数 重复数处理: 使i为左至右第一个不重复数:while(i != 0 && i<n-2 && a[i] == a[i-1]) i++; 使r为右至左第一个不重复数(原序最后一个):while(r>i && r+1<n && a[r] == a[r+1]) r--; 15. 3Sum…

参考资料: https://leetcode.com/problems/3sum/discuss/7402/Share-my-AC-C%2B%2B-solution-around-50ms-O(N*N)-with-explanation-and-comments https://www.cnblogs.com/grandyang/p/4481576.html class Solution { public: vector<vector<int>> threeSum(vector&l…

一.题目链接:https://leetcode.com/problems/3sum/ 二.题目大意: 3和问题是一个比较经典的问题,它可以看做是由2和问题(见http://www.cnblogs.com/wangkundentisy/p/7525356.html)演化而来的.题目的具体要求如下: 给定一个数组A,要求从A中找出这么三个元素a,b,c使得a + b + c = 0,返回由这样的a.b.c构成的三元组,且要保证三元组是唯一的.(即任意的两个三元组,它们里面的元素不能完全相同) 三.题…

题目 Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-…

题目链接 https://leetcode.com/problems/3sum/?tab=Description   Problem: 给定整数集合,找到所有满足a+b+c=0的元素组合,要求该组合不重复.   首先对给出的数组进行排序 Arrays.sort() 从第0个元素开始进行判断,对应的有最大值num[high] 1.当num[low]+num[high]== -num[i]时,此时可以将num[low],num[high],num[i]添加至list中     a. 当low<hig…

我现在在做一个叫<leetbook>的免费开源书项目,力求提供最易懂的中文思路,目前把解题思路都同步更新到gitbook上了,需要的同学可以去看看 书的地址:https://hk029.gitbooks.io/leetbook/ 015. 3Sum 问题 Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the…

Two Sum: 解法一:排序后使用双索引对撞:O(nlogn)+O(n) = O(nlogn) , 但是返回的是排序前的指针. 解法二:查找表.将所有元素放入查找表, 之后对于每一个元素a,查找 target-a 是否存在.使用map实现,键是元素的值,键值是元素对应的索引. 不能把vector中所有的值放到查找表中,因为若有重复的值,前一个会被后一个覆盖.所以改善为把当前元素v前面的元素放到查找表中. 时间复杂度:O(n) 空间复杂度:O(n) 注意:这道题只有唯一解. class Solu…

1. 原题链接 https://leetcode.com/problems/3sum/description/ 2. 题目要求 数组S = nums[n]包含n个整数,请问S中是否存在a,b,c三个整数,使得a+b+c=0.找出所有满足该条件的三元组,且不包含重复三元组. 3. 解题思路 首先对数组进行排序 思路一:三层for循环暴力解决,同时考虑过滤重复,时间复杂度为O(n3) 思路二:时间复杂度为O(n2),外面一层for循环,以每个元素 nums[i] 作为三元组重的一个元素,然后从剩余的…

3Sum  Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The…

3sum: 1 class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { vector<vector<int>>result; vector<vector<int>>::iterator iter; vector<int>Middle; ; sort(nums.begin(),nums.end()); ;i<…

作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 个人公众号:负雪明烛 本文关键词:3sum, 三数之和,题解,leetcode, 力扣,Python, C++, Java 题目地址: https://leetcode.com/problems/3sum/description/ 题目描述: Given an array nums of n integers, are there elements a, b, c in nums suc…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-1,…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The solut…

题目: Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The s…

题目描述: Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. 解题分析: 这道题注意一下几点即可: 1,先固定前两个数的位置,移动第三个数,这样的查找方式不会有数字组合的遗漏: 2,要考虑到数组元素有重复的情况下的处理. 3,若先为数组排…

问题描述: Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The…

题目意思:给一个乱序数组,在里面寻找三个数之和为0的所有情况,这些情况不能重复,增序排列 思路:前面2sum,我用的是map,自然那道题map比双指针效率高,这道题需要先排序,再给三个指针,i.j.k 对于i指针从前往后遍历,对于一个固定的i指针,其实就是2Sum的情况,给定一前一后两个指针进行遍历, 值大了,就把后面的指针往前移,值小了就把前面的指针往后移. 比较麻烦的地方在于去重,首先是i指针的去重,j和k只用一个去重就可以了 ps:这是数组中一种十分常用的方法. class Solutio…

题目链接 给n个数, 找出三个数相加结果为0的所有的组, 不可重复. 用双指针的思想,O(n^2)暴力的找, 注意判重复. class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { int sz = nums.size(); vector <vector<int> > ans; vector <int> tmp; sort(nums.b…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-1,…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-1,…

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. For example, given array S = [-1,…

一天一道LeetCode系列 (一)题目 Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. For example, given array S = {-1 0 1 2 -1 -4}, A solution set is: (-1, 0,…