LeetCode-in-All

560. Subarray Sum Equals K

Medium

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

Solution

from collections import defaultdict

class Solution:
    def subarraySum(self, nums: List[int], k: int) -> int:
        tempSum = 0
        ret = 0
        sumCount = defaultdict(int)
        sumCount[0] = 1
        
        for i in nums:
            tempSum += i
            if tempSum - k in sumCount:
                ret += sumCount[tempSum - k]
            sumCount[tempSum] += 1
        
        return ret

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