Create 974-subarray-sums-divisible-by-k.js

Author: everthis

974-subarray-sums-divisible-by-k.js

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+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number}
+ */
+const subarraysDivByK = function (nums, k) {
+  const memo = {0: 1}
+  let sum = 0, res = 0
+  for(const e of nums) {
+    sum += e
+    const remain = ( sum % k + k) % k
+    res += memo[remain] ?? 0
+    memo[remain] = (memo[remain] ?? 0) + 1 
+  }
+  return res
+}