I found summary of k Sum problem and solutions in leetcode on the Internet. http://www.sigmainfy.com/blog/summary-of-ksum-problems.html…

K SUM My Submissions http://www.lintcode.com/en/problem/k-sum/ 题目来自九章算法 13% Accepted Given n distinct positive integers, integer k (k <= n) and a number target. Find k numbers where sum is target. Calculate how many solutions there are? Example Given…

k Sum Given n distinct positive integers, integer k (k <= n) and a number target. Find k numbers where sum is target. Calculate how many solutions there are? Example Given [1,2,3,4], k = 2, target = 5. There are 2 solutions: [1,4] and [2,3]. Return 2…

转自  http://tech-wonderland.net/blog/summary-of-ksum-problems.html 前言: 做过leetcode的人都知道, 里面有2sum, 3sum(closest), 4sum等问题, 这些也是面试里面经典的问题, 考察是否能够合理利用排序这个性质, 一步一步得到高效的算法. 经过总结, 本人觉得这些问题都可以使用一个通用的K sum求和问题加以概括消化, 这里我们先直接给出K Sum的问题描述和算法(递归解法), 然后将这个一般性的方法套用…

算是经典算法问题了.这里主要针对只存在一个解或者只需要求一个解的情况描述一下解题思路.若需要找到所有可能解,方法需要略作调整.如有问题,欢迎指正. 2 sum: 如果已排序,可直接用夹逼法,即两指针从头尾向中间移动,使和靠近target.时间复杂度为O(n). 若未排序,因为除非有特别限制,比较排序的时间复杂度为O(nlgn).此时用hash更为合适,可以达到O(n)的时间复杂度.此方法实际上对已排序数组也实用.步骤如下: 每一个数a在放入hash表前,判断目标target-a是否在hash 表…

前言: 这几天在做LeetCode 里面有2sum, 3sum(closest), 4sum等问题, 这类问题是典型的递归思路解题.该这类问题的关键在于,在进行求和求解前,要先排序Arrays.sort()可实现,而本文则着重探讨关于KSum问题. leetcode求和问题描写叙述(K sum problem): K sum的求和问题通常是这样子描写叙述的:给你一组N个数字(比方 vector num), 然后给你一个常数(比方 int target) ,我们的goal是在这一堆数里面找到K个数…

目录 题目链接 思路 代码 题目链接 传送门 思路 首先我们将原式化简: \[ \begin{aligned} &\sum\limits_{l_1=1}^{n}\sum\limits_{l_2=1}^{n}\dots\sum\limits_{l_k=1}^{n}gcd(l_1,l_2,\dots,l_k)^2&\\ =&\sum\limits_{d=1}^{n}d^2\sum\limits_{l_1=1}^{n}\sum\limits_{l_2=1}^{n}\dots\sum\li…

K Sum 终于过了这玩意啊啊啊==== 莫比乌斯反演,杜教筛,各种分块,积性函数怎么线性递推还很迷==,得继续研究研究 #include<bits/stdc++.h> using namespace std; #define int long long #define maxn 1000000+10 int P[maxn],g[maxn]; bool vis[maxn]; unordered_map<int,int> mp; int T,n,k; ); ; void init()…

Description: 定义函数 \[ f _n (k) = \sum _{l _1 = 1} ^n \sum _{l _2 = 1} ^n \cdots \sum _{l _k = 1} ^n \gcd(l _1, l _2, \cdots, l _k) ^2 \] 现给定 \(n, k\),需要求出 \(\sum _{i = 2} ^k f _n (i)\),答案对 \(10 ^9 + 7\) 取模. \(T\) 组数据. \[ 1 \le T \le 10, 1 \le n \le 10…

List<List<Integer>> kSum_Trim(int[] a, int target, int k) { List<List<Integer>> result = new ArrayList<>(); if (a == null || a.length < k || k < 2) return result; Arrays.sort(a); kSum_Trim(a, target, k, 0, result, new A…

转自:http://tech-wonderland.net/blog/summary-of-ksum-problems.html (中文旧版)前言: 做过leetcode的人都知道, 里面有2sum, 3sum(closest), 4sum等问题, 这些也是面试里面经典的问题, 考察是否能够合理利用排序这个性质, 一步一步得到高效的算法. 经过总结, 本人觉得这些问题都可以使用一个通用的K sum求和问题加以概括消化, 这里我们先直接给出K Sum的问题描述和算法(递归解法), 然后将这个一般性…

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…

Given n unique integers, number k (1<=k<=n) and target. Find all possible k integers where their sum is target. Example Given [1,2,3,4], k=2, target=5, [1,4] and [2,3] are possible solutions. 这道题同Combination Sum II public class Solution { /** * @par…

题目描述 Consider a triangle of integers, denoted by T. The value at (r, c) is denoted by Tr,c , where 1 ≤ r and 1 ≤ c ≤ r. If the greatest common divisor of r and c is exactly 1, Tr,c = c, or 0 otherwise.Now, we have another triangle of integers, denote…

Great great DP learning experience:http://www.cnblogs.com/yuzhangcmu/p/4279676.html Remember 2 steps of DP: a) setup state transfer equation; b) setup selection strategy. a) States From problem statement, we find 3 variables: array size, k and target…

题目: k数和 II 给定n个不同的正整数,整数k(1<= k <= n)以及一个目标数字. 在这n个数里面找出K个数,使得这K个数的和等于目标数字,你需要找出所有满足要求的方案. 样例 给出,返回 [[1,4],[2,3]] 解题: 题目中限制的条件很多,A数组中的各个数字都不相等,A中k个数的和是 target 问题: 1.在所有的组合方式中,A[i] 是否会重复,也就是说,A[i] ,即在{a,b,A[i]} 也在{a1,b1,A[i]}中. 可能:如A = {1,2,3,4,5} 3个…

没通过的代码: class Solution { public: /* * @param A: An integer array * @param k: A positive integer (k <= length(A)) * @param target: An integer * @return: An integer */ int kSum(vector<int> &A, int k, int target) { // write your code here int le…

Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k. Example: Given matrix = [ [1, 0, 1], [0, -2, 3] ] k = 2 The answer is 2. Because the sum of rectangle [[0, 1], […

题目描述: Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k. 解题思路: 根据题意,寻找二维数组中所有可以组成的矩形中面积不超过k的最大值,所以必须要求出可能组成的矩形的面积并与k比较求出最终结果.这里为了最终不超时,可以在一下方面进行优化: 1.设置一个数组比较当前列(或…

Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into knon-empty subsets whose sums are all equal. Example 1: Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4 Output: True Explanation: It's possible…

Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into k non-empty subsets whose sums are all equal. Example 1: Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4 Output: True Explanation: It's possible…

［抄题］: Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into knon-empty subsets whose sums are all equal. Example 1: Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4 Output: True Explanation: It's pos…

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k. Example 1: Input:nums = [1,1,1], k = 2 Output: 2 Note: The length of the array is in range [1, 20,000]. The range of numbers…

Problem Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into k non-empty subsets whose sums are all equal. Example 1:Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4Output: TrueExplanation: It's pos…

Given a non-empty 2D matrix matrix and an integer k, find the max sum of a rectangle in the matrix such that its sum is no larger than k. Example: Input: matrix = [[1,0,1],[0,-2,3]], k = 2 Output: 2 Explanation: Because the sum of rectangle [[0, 1],…

整体上3个题都是求subarray,都是同一个思想,通过累加,然后判断和目标k值之间的关系,然后查看之前子数组的累加和. map的存储:560题是存储的当前的累加和与个数 561题是存储的当前累加和的余数与第一次出现这个余数的位置 325题存储的是当前累加和与第一次出现这个和的位置 其实561与325都是求的最长长度,那就一定要存储的是第一次出现满足要求的位置,中间可能还出现这种满足要求的情况,但都不能进行存储 560. Subarray Sum Equals K 求和为k的连续子数组的个数 h…

Given an array of integers nums and a positive integer k, find whether it's possible to divide this array into k non-empty subsets whose sums are all equal. Example 1: Input: nums = [4, 3, 2, 3, 5, 2, 1], k = 4 Output: True Explanation: It's possible…

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 暴力求解 日期 题目地址:https://leetcode-cn.com/problems/two-sum-less-than-k/ 题目描述 Given an array A of integers and integer K, return the maximum S such that there exists i < j with A[i] +…

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 回溯法 日期 题目地址:https://leetcode.com/problems/partition-to-k-equal-sum-subsets/description/ 题目描述 Given an array of integers nums and a positive integer k, find whether it's possibl…

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive. The update(i, val) function modifies nums by updating the element at index i to val. Example: Given nums = [1, 3, 5] sumRange(0, 2) -> 9 update(1, 2…