add new solutions

solutions/4/q448/solution.go

@@ -0,0 +1,22 @@
+package q448
+
+func findDisappearedNumbers(nums []int) []int {
+	n := len(nums)
+	ret := make([]int, n)
+	for i := range ret {
+		ret[i] = i + 1
+	}
+	for _, num := range nums {
+		ret[num-1] = -1
+	}
+	p := 0
+	for i := range ret {
+		if ret[i] != -1 {
+			ret[p] = ret[i]
+			p++
+		}
+	}
+	return ret[:p]
+}
+
+var _ = findDisappearedNumbers