add new solutions

solutions/0/q22/solution.go

@@ -0,0 +1,27 @@
+package q22
+
+func gen(n, lvl, used int, buf []byte, ret []string) []string {
+	if buf == nil {
+		buf = make([]byte, 0, n*2)
+	}
+	if len(buf) == n*2 {
+		return append(ret, string(buf))
+	}
+
+	if used < n {
+		buf = append(buf, '(')
+		ret = gen(n, lvl+1, used+1, buf, ret)
+		buf = buf[:len(buf)-1]
+	}
+	if lvl > 0 {
+		buf = append(buf, ')')
+		ret = gen(n, lvl-1, used, buf, ret)
+	}
+	return ret
+}
+
+func generateParenthesis(n int) []string {
+	return gen(n, 0, 0, nil, nil)
+}
+
+var _ = generateParenthesis