Subarray Sum Equals K

Description

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

 

Constraints:

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

Solution(javascript)

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var subarraySum = function(nums, k) {
    const map = {
        0: 1
    }
    let sum = 0
    let count = 0
    for(let num of nums) {
        sum += num
        if(map[sum-k] > 0) {
            count += map[sum-k]
        }
        map[sum] = (map[sum] || 0) + 1
    }
    return count 
};