README_EN.md

560. Subarray Sum Equals K

中文文档

Description

Given an array of integers nums and an integer k, return the total number of continuous subarrays whose sum equals to k.

 

Example 1:

Input: nums = [1,1,1], k = 2
Output: 2

Example 2:

Input: nums = [1,2,3], k = 3
Output: 2

 

Constraints:

• 1 <= nums.length <= 2 * 104
• -1000 <= nums[i] <= 1000
• -107 <= k <= 107

Solutions

Python3

class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        mp = collections.Counter()
        mp[0] = 1
        res = s = 0
        for num in nums:
            s += num
            res += mp[s - k]
            mp[s] += 1
        return res

Java

class Solution {
    public int subarraySum(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        map.put(0, 1);
        int res = 0;
        int s = 0;
        for (int num : nums) {
            s += num;
            res += map.getOrDefault(s - k, 0);
            map.put(s, map.getOrDefault(s, 0) + 1);
        }
        return res;
    }
}

TypeScript

function subarraySum(nums: number[], k: number): number {
    let ans = 0, pre = 0;
    let hashTable = new Map();
    hashTable.set(0, 1);
    for (let num of nums) {
        pre += num;
        ans += (hashTable.get(pre - k) || 0);
        hashTable.set(pre, (hashTable.get(pre) || 0) + 1);
    }
    return ans;
};

C++

class Solution {
public:
    int subarraySum(vector<int>& nums, int k) {
        unordered_map<int, int> mp;
        mp[0] = 1;
        int res = 0, s = 0;
        for (int num : nums)
        {
            s += num;
            res += mp[s - k];
            ++mp[s];
        }
        return res;
    }
};

Go

func subarraySum(nums []int, k int) int {
	mp := make(map[int]int)
	mp[0] = 1
	res, s := 0, 0
	for _, num := range nums {
		s += num
		res += mp[s-k]
		mp[s]++
	}
	return res
}

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