【easy】532. K-diff Pairs in an Array

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【easy】532. K-diff Pairs in an Array

这道题给了我们一个含有重复数字的无序数组,还有一个整数k,让我们找出有多少对不重复的数对(i, j)使得i和j的差刚好为k.由于k有可能为0,而只有含有至少两个相同的数字才能形成数对,那么就是说我们需要统计数组中每个数字的个数.我们可以建立每个数字和其出现次数之间的映射,然后遍历哈希表中的数字,如果k为0且该数字出现的次数大于1,则结果res自增1:如果k不为0,且用当前数字加上k后得到的新数字也在数组中存在,则结果res自增1,参见代码如下: /* 思路:因为存在k=0的情况,并且答案需要是完…

【easy】215. Kth Largest Element in an Array 第K大的数

class Solution { public: int quicksort(vector<int>& nums, int start, int end, int k){ int i = start; int j = end; int x = nums[i]; while (i<j){ //快排核心… while (nums[j]<x && i<j) j--; if (i<j) nums[i++] = nums[j]; while (nums[i…

661. Image Smoother【easy】

661. Image Smoother[easy] Given a 2D integer matrix M representing the gray scale of an image, you need to design a smoother to make the gray scale of each cell becomes the average gray scale (rounding down) of all the 8 surrounding cells and itself.…

189. Rotate Array【easy】

189. Rotate Array[easy] Rotate an array of n elements to the right by k steps. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. Note:Try to come up as many solutions as you can, there are at least 3 differen…

561. Array Partition I【easy】

561. Array Partition I[easy] Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible. Example 1: Inpu…

219. Contains Duplicate II【easy】

219. Contains Duplicate II[easy] Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k. 错误解法: class Solut…