Submission #1691229

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Source Code Expand

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>

using namespace std;

inline int read()
{
	int x=0;char ch=getchar();
	while(ch<'0' || '9'<ch)ch=getchar();
	while('0'<=ch && ch<='9')x=x*10+(ch^48),ch=getchar();
	return x;
}

const int N=1e5+9;

unsigned int bit[N];
int n,f[N],ans;
int to[N<<1],nxt[N<<1],beg[N],tot;

inline void add(int u,int v)
{
	to[++tot]=v;
	nxt[tot]=beg[u];
	beg[u]=tot;
}

inline void dfs(int u,int fa)
{
	bit[u]=f[u]=0;
	int las=0;
	for(int i=beg[u],v;i;i=nxt[i])
		if((v=to[i])!=fa)
		{
			dfs(v,u);
			las|=bit[v]&bit[u];
			bit[u]|=bit[v];
		}
	if(bit[u]==0)
		bit[u]=1;
	else
	{
		while((1<<f[u])<las || bit[u]&(1<<f[u]))f[u]++;
		bit[u]=(bit[u]>>f[u]<<f[u])|(1<<f[u]);
	}
	if(ans<f[u])ans=f[u];
}

int main()
{
	if(fopen("vj.in","r"))
	{
		freopen("vj.in","r",stdin);
		freopen("vj.out","w",stdout);
	}

	n=read();
	for(int i=1,u,v;i<n;i++)
	{
		u=read();v=read();
		add(u,v);add(v,u);
	}

	dfs(1,0);
	printf("%d\n",ans);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:55:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result]
   freopen("vj.in","r",stdin);
                             ^
./Main.cpp:56:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result]
   freopen("vj.out","w",stdout);
                               ^

Judge Result