[Data structure template question] DFS (depth first search) seeking 1-n full array

#include<bits/stdc++.h>
using namespace std;
int a[100001],n;
int book[100001];
void dfs(int step){
	if(step==n+1){
		for(int i=1;i<=n;i++) printf("%d ",a[i]);
		cout<<endl;
		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;
}

Below is the board with comments:

#include<iostream>
using namespace std;
int a[100001],n;
int book[100001];//判断是否被访问 
void dfs(int step){
	// if(满足所需要的条件)   {  相应的操作；return；} 
	if(step==n+1){
		for(int i=1;i<=n;i++) printf("%d ",a[i]);//打印 
		cout<<endl;
		return; 
	}
	//枚举 
	for(int i=1;i<=n;i++)
	{
		if(book[i]==0)
		{
			a[step]=i;//记录数据 
			book[i]=1;//记录相应的数已经被访问
			dfs(step+1);//进一步搜索 
			book[i]=0;//恢复到未被访问 
		}
	}
}
int main(){
	cin>>n;
	dfs(1);//从一开始搜索并且打印 
	return 0;
}