生成全排列

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<algorithm>
#include<fstream>
using namespace std;
const int maxn = 50;

int a[maxn];
bool vis[maxn];

void permutation(int *a,int curr,int n){
	if (curr == n){
		for (int i = 0; i < n; i++)
			printf("%d ", a[i]);
		printf("
");
		return;
	}
	for (int i = 1; i <= n; i++){
		if (!vis[i]){
			vis[i] = 1;     //标记访问
			a[curr] = i;
			permutation(a, curr + 1, n);
			vis[i] = 0;      //撤销标志
		}
	}
}
/*STL函数next_permutation是按照字典序求下一个排列，可以处理元素重复的情况。
---*/
void permutation(int*a,int n){
	sort(a, a + n);
	do{
		for (int i = 0; i < n; i++)printf("%d ", a[i]);
		printf("
");
	} while (next_permutation(a, a + n));
}

int main(){
	int n;

	int p[5] = { 2, 5, 1, 7, 2 };
	permutation(p, 5);

	while (~scanf("%d", &n)){
		memset(vis,0, sizeof(vis));
		permutation(a,0,n);
	}
	return 0;
}