/* Permutation */ void permu(int n, int r, int idx){ if (idx == r){ for (int i = 0; i < r; ++i) printf("%c ", buf[i]); printf("\n"); } for (int i = 0; i < n; ++i){ if (used[i]) continue; used[i] = 1; buf[idx] = str[i]; permu(n, r, idx + 1); used[i] = 0; } } /* Combination */ void combi(int n, int r, int s, int idx) { if (idx == r){ for (int i = 0; i < r; ++i) printf("%..