add new solutions

solutions/2/q219/solution.go

@@ -0,0 +1,18 @@
+package q219
+
+func containsNearbyDuplicate(nums []int, k int) bool {
+	seen := make(map[int]struct{}, k)
+
+	for i, num := range nums {
+		if _, ok := seen[num]; ok {
+			return true
+		}
+		seen[num] = struct{}{}
+		if i >= k {
+			delete(seen, nums[i-k])
+		}
+	}
+	return false
+}
+
+var _ = containsNearbyDuplicate