Continuous Subarray Sum

Author: charlesbuczel

0523_continuousSubarraySum.js

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+/**
+ * @param {number[]} nums Array of integers.
+ * @param {number} target Sum target of subarray elements.
+ * @return {boolean} True if subarray of at least length 2 exists which elements add up to target
+ * @summary Two Sum {@link https://leetcode.com/problems/continuous-subarray-sum/}
+ * @description Given an array of integers, return indices of the two numbers such that they add up to a specific target.
+ * Space O(t) - dictionary with at most size of target entries.
+ * Time O(n) - we iterate through nums array once.
+ */
+const checkSubarraySum = (nums, target) => {
+  const lookup = { 0: -1 };
+  let movingModulo = 0;
+
+  for (let index = 0; index < nums.length; index++) {
+    movingModulo += nums[index];
+    if (target !== 0) movingModulo = movingModulo % target;
+
+    if (lookup[movingModulo] !== undefined) {
+      if (index - lookup[movingModulo] >= 2) return true;
+    } else lookup[movingModulo] = index;
+  }
+
+  return false;
+};