[summer daily question] Luogu p1706 full ranking question

Topic link ：P1706 The total permutation problem - Luogu | New ecology of computer science education (luogu.com.cn)

Title Description

Output natural numbers in dictionary order 1  To n  All the non repetitive permutations , namely n  The whole arrangement , It is required that no duplicate number is allowed in any number sequence generated .

Input format

An integer n.

Output format

from 1 ~ n  A sequence of all the numbers that do not repeat , One sequence per line .

Keep every number 5  Field width .

Examples #1

The sample input #1

3

Sample output #1

1    2    3
1    3    2
2    1    3
2    3    1
3    1    2
3    2    1

Tips

1 <= n <= 9.

AC code 1:（DFS）

#include<iostream>

using namespace std;

int n;
int a[10],book[10];

void dfs(int step)
{
	if(step==n+1)
	{
		for(int i=1;i<=n;i++)
			printf("%5d",a[i]);
		puts("");
		
		return ;
	}
	for(int i=1;i<=n;i++)
	{
		if(book[i]==0)
		{
			a[step]=i;
			book[i]=1;
			dfs(step+1);
			book[i]=0;
		}
	}
	return ;
}

int main()
{
	cin>>n;
	dfs(1);
	
	return 0;
}

AC code 2:（STL-next_permutation）

#include<iostream>
#include<algorithm>

using namespace std;

int main()
{
	int n;
	cin>>n;
	string s="123456789";
	do{
		for(int i=0;i<n;i++)
			printf("%5c",s[i]);
		puts("");
	}while(next_permutation(s.begin(),s.begin()+n));
}