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#include <bits/stdc++.h>
using namespace std;
const int N = 10;
int a[N];
bool st[N];
int n = 3;
//函数说明：填充第几个盒子
void dfs(int step) {
//如果全部填充完毕，走到了最后虚拟的n+1号盒子面前，就表示前面都完成了正确填充
if (step == n + 1) {
for (int i = 1; i <= n; i++) cout << a[i] << " ";
cout << endl;
return;
}
//每一个数字都可以用来填充
for (int i = 1; i <= n; i++)
//如果没有使用过
if (!st[i]) {
//放里
a[step] = i;
//标识已使用
st[i] = true;
//填充下一个
dfs(step + 1);
//标识未使用
st[i] = false;
int main() {
//开始填充第一个盒子
dfs(1);
return 0;
