【递归】n个数的集合的所有子集， 去掉重复的项

输入：

3

1 1 3

输出：

1

1 1

1 1 3

1 3

3

Delphi代码：

unit unrepeat_combination;

const
  max_n = 10;

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

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

  for i := p to m - 1 do //共m个不同的数
    if used[i] > 0 then
    begin
      Dec(used[i]);
      rcd[index] := num[i];
      unrepeat_combination(index + 1, i); //因为used[i]可能大于0， 所以这里不能用 i+1
      Inc(used[i]);
    end;
end;

var
  i, j, val: integer;
begin
  while not seekeof do
  begin
    readln(n);
    m := 0;
    for i := 0 to n - 1 do
    begin
      Read(val);
      j := 0;
      while j < m do
      begin
        if val = num[j] then
        begin
          Inc(used[j]);
          break;
        end;
        Inc(j);
      end;
      if j = m then
      begin
        used[m] := 1;
        num[m] := val;
        Inc(m);
      end;
    end;
    unrepeat_combination(0, 0);
  end;
end.

C++代码：

#include <stdio.h>
#define MAX_N 10

int rcl[MAX_N], num[MAX_N], used[MAX_N];
int m,n;

void unrepeat_combination(int index, int p)
{
    int i;
    for (i=0; i<index; i++)
    {
        printf("%d", rcl[i]);
        if (i<index-1)
        {
            printf(" ");
        }
        else
            printf("\n");
    }

    for (i=p; i<n; i++)
    {

        if (used[i]>0)
        {
            used[i]--;
            rcl[index] = num[i];
            unrepeat_combination(index+1, i);
            used[i]++;
        }
    }
}

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

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