【递归】n个数的全排列

输入：

3

1 2 3

输出：

1 2 3

1 3 2

2 1 3

2 3 1

3 1 2

3 2 1

Delphi代码：

program full_permutation;
//全排列

const
  max_n = 10;

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

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

  for i := 0 to n - 1 do
    if used[i] = 0 then
    begin
      used[i] := 1;
      rcd[index] := num[i];
      full_permutation(i + 1);
      used[i] := 0;
    end;
end;

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

C++代码：

#include <stdio.h>
#include <string.h>
#define  MAX_N 10

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

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

    for (i=0; i<n; i++)
    {
        if (!used[i])
        {
            used[i] = 1;  //标记
            rcd[index] = num[i];  //在index位置上放上该数
            full_permutation(index+1);
            used[i] = 0;  //清除标记
        }
    }
}

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

void main()
{
    while(read_data())
    {
        full_permutation(0);
    }
}