Finding all combinations of well-formed brackets

Question

This came up while talking to a friend and I thought I\'d ask here since it\'s an interesting problem and would like to see other people\'s solutions.

The task is to

Answer 1

public static void printAllValidBracePermutations(int size) {
    printAllValidBracePermutations_internal("", 0, 2 * size);
}

private static void printAllValidBracePermutations_internal(String str, int bal, int len) {
    if (len == 0) System.out.println(str);
    else if (len > 0) {
        if (bal <= len / 2) printAllValidBracePermutations_internal(str + "{", bal + 1, len - 1);
        if (bal > 0) printAllValidBracePermutations_internal(str + "}", bal - 1, len - 1);
    }
}