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Subarray Sum Equals K

Problem statement​

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

Example 1:

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

Example 2:

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

Constraints:

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

My solution​

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
var subarraySum = function(nums, k) {
    let memo = new Map();
    let sum = 0;
    let count = 0;
    
    memo.set(0, 1)
    
    for (const num of nums) {
        sum += num
        
        const diff = sum - k;
        
        // console.log("diff", diff)
        // console.log("count", count)
        
        if (memo.has(diff)) {
            count += memo.get(diff)
        }
        
        memo.set(sum, (memo.get(sum) || 0) + 1)
        
        // console.log(memo, sum)
    }
    
    return count;
};