Subarray Sum Equals K

Author: charlesbuczel

0560_subarraySumEqualsK.js

@@ -0,0 +1,25 @@
+/**
+ * @param {number[]} nums Array of numbers.
+ * @param {number} k Goal sum of valid subarray.
+ * @return {number} Count of subarrays for which elements sum up to k.
+ * @summary Subarray Sum Equals K {@link https://leetcode.com/problems/subarray-sum-equals-k/}
+ * @description Given array of integers and goal sum, return number of subarrays for which sum of elements equal k.
+ * Space O(n) - Creating object literal (hashmap) with up to n keys.
+ * Time O(n) - Input is traversed nums.length times.
+ */
+const subarraySum = (nums, k) => {
+  let count = 0;
+  let sum = 0;
+  const results = {
+    0: 1,
+  };
+
+  const length = nums.length;
+  for (let i = 0; i < length; i++) {
+    sum += nums[i];
+    if (results[sum - k]) count += results[sum - k];
+    results[sum] = results[sum] ? results[sum] + 1 : 1;
+  }
+
+  return count;
+};