/*
 * combination.cpp
 *
 *  Created on: 2011/3/25
 *      Author: dirk
 */
// for convenience, indexing in this alg. starts from 1
 
#include <iostream>
using namespace std;
 
#define MAX 512
 
inline int advance_and_relax(int digits[], int m, int n) {
    if(n == 1) return 0; // no way to advance
    for(int i = n - 1; i >= 1; --i) {
        if(++digits[i] <= (m - n + i)) { // digits[i] is able to advance
            for(int cur_index = i+1, cur_value = digits[i]+1; cur_index <= n; ++cur_index) { // we relax all digits behind digits[i]
                digits[cur_index] = cur_value++;
            }   
            return 1;
        }   
    }   
    return 0;
}
 
inline void C(int x[], int m, int n) {
    int digits[MAX+1]; // our indexing starts from 1
    for(int i = 0; i < n + 1; ++i) digits[i] = i; // initialization
    int finish = 0;
    while(finish == 0) {
        for(int i = 1; i <= n; ++i) cout << x[digits[i]] << ' ';
        cout << '\n';
        if(++digits[n] > m) {
            if(advance_and_relax(digits, m, n) == 1) finish = 0;
            else finish = 1;
        }   
    }   
}
 
int main() {
    int m, n;
    int x[MAX+1];
    cout << "M = ? ";
    cin >> m;
    cout << "N = ? ";
    cin >> n;
    cout << "輸入 M 個數字: ";
    for(int i = 1; i <= m; ++i) cin >> x[i];
    if(m < n || m <=0 || n <= 0 || m > 512) {
        cout << "輸入格式不正確, 界線條件是 M > N 且 M, N > 0\n"
             << "記憶體限制是 M 必須小於等於 512\n"
             << "真的 M 太大也會算很久怕你沒耐心XD\n";
        return -1;
    }
    C(x, m, n);
}