CF1172A Nauuo and Cards 贪心

Posted 2020-11-26 guangheli

我们发现，如果我们打数字牌后，就不能打 0 了.  

分两种情况讨论即可. 

code: 

#include <bits/stdc++.h>  
#define N 200008 
#define ll long long  
#define setIO(s) freopen(s".in","r",stdin) 
using namespace std;  
int n;  
int a[N],b[N];  
set<int>se;     
set<int>::iterator it;  
int check() 
{  
	int i,j,flag=0,cur,tp=1;       
	if(!b[n]) return 0;     
	for(i=n-1;i>=0;--i)  
		if(!b[i]||(b[i]!=b[i+1]-1)) 
		{
			if(b[i+1]!=1)  
				flag=1;  
			break;  
		}   
	if(flag)   
		return 0;    
	if(b[n]==n)    
	{
		printf("0
");    
		return 1;  
	}                       
	cur=b[n]+1;  
	for(i=1;i<=n;++i)  
		if(a[i]) se.insert(a[i]);          
	while(cur<=n) 
	{
		if(se.empty()) 
			return 0;    
		it=se.begin();   
		if(*it==cur)   
		{
			se.erase(it);   
			++cur; 
			if(b[tp])se.insert(b[tp]);     
			++tp;  
		}
		else return 0;   
	}   
	printf("%d
",n-b[n]);     
	return 1;   
}
int main() 
{ 
	// setIO("input"); 
	int i,j;              
	scanf("%d",&n);  
	for(i=1;i<=n;++i)
		scanf("%d",&a[i]);  
	for(i=1;i<=n;++i) 
		scanf("%d",&b[i]);    
	if(!check())         
	{    
		int MAX=0;   
		for(i=1;i<=n;++i)                 
			if(b[i]) MAX=max(MAX,i-b[i]+1);   
		printf("%d
",MAX+n);   
	}   
	return 0;  
}