go: add «974. Subarray Sums Divisible by K»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/subarray-sums-divisible-by-k.go

@@ -0,0 +1,18 @@
+package subarray_sums_divisible_by_k
+
+func subarraysDivByK(nums []int, k int) int {
+	counters := make([]int, k)
+	counters[0] = 1
+
+	total := 0
+
+	runningMod := 0
+	for _, num := range nums {
+		runningMod = (k + runningMod + num%k) % k
+
+		total += counters[runningMod]
+		counters[runningMod]++
+	}
+
+	return total
+}