Leetcode 560. Subarray Sum Equals K

Subarray Sum Equals K

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 = 2Output: 2

Note:

1. The length of the array is in range [1, 20,000].
2. The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].

思路：
（待补充）

class Solution {    public int subarraySum(int[] nums, int k) {        HashMap<Integer, Integer> map = new HashMap();        map.put(0, 1);        int sum = 0;        int result = 0;        for(int i = 0; i < nums.length; i++) {            sum += nums[i];            if(map.containsKey(sum - k)) {                result += map.get(sum-k);             }            map.put(sum, map.getOrDefault(sum, 0) + 1);        }        return result;    }}