【递归】n个数中m个数的组合

输入：

4 3

1 2 3 4

输出：

1 2 3

1 2 4

1 3 4

2 3 4

Delphi代码：

program select_combination;

const
  max_n = 10;

var
  n, m: integer;
  rcd, num: array[0..max_n] of integer;

procedure select_combination(index, p: integer);
var
  i: integer;
begin
  if index = m then
  begin
    for i := 0 to m - 2 do
      Write(rcd[i], ' ');
    writeln(rcd[m - 1]);
    exit;
  end;

  for i := p to n - 1 do
  begin
    rcd[index] := num[i];
    select_combination(index + 1, i + 1);
  end;
end;

var
  i: integer;
begin
  while not seekeof do
  begin
    readln(n, m);
    for i := 0 to n - 1 do
      Read(num[i]);
    select_combination(0, 0);
  end;
end.

C++代码：

#include <stdio.h>
#define MAX_N 10

int rcd[MAX_N], num[MAX_N];
int n,m;

void select_combination(int index, int p)
{

    int i;
    if (index == m)
    {
        for (i=0; i<m; i++)
        {
            printf("%d", rcd[i]);
            if (i<m-1)
            {
                printf(" ");
            }
        }
        printf("\n");
        return;
    }

    for (i=p; i<n; i++)
    {
        rcd[index] = num[i];
        select_combination(index+1, i+1);
    }
}

int read_data()
{
    int i;
    if (scanf("%d%d", &n, &m)==EOF)
    {
        return 0;
    }
    for (i=0; i<n; i++)
    {
        scanf("%d", &num[i]);
    }
    return 1;
}



void main()
{
    while(read_data())
    {
        select_combination(0, 0);
    }
}