Submission #1611651

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Source Code Expand

#include<cstdio>
#include<algorithm>
using namespace std;
inline int read()
{
	int x;char c;
	while((c=getchar())<'0'||c>'9');
	for(x=c-'0';(c=getchar())>='0'&&c<='9';)x=x*10+c-'0';
	return x;
}
#define MN 100000
struct edge{int nx,t;}e[MN*2+5];
int h[MN+5],en,f[MN+5];
inline void ins(int x,int y)
{
	e[++en]=(edge){h[x],y};h[x]=en;
	e[++en]=(edge){h[y],x};h[y]=en;
}
int cal(int x){for(int i=17;i;--i)if(x&(1<<i))return i;return -1;}
void dfs(int x,int fa)
{
	int mx=0;
	for(int i=h[x];i;i=e[i].nx)if(e[i].t!=fa)
	{
		dfs(e[i].t,x);
		mx=max(mx,cal(f[x]&f[e[i].t])+1);
		f[x]|=f[e[i].t];
	}
	for(int i=0;;++i)if(i>=mx&&!(f[x]&(1<<i)))
		{f[x]=(f[x]|(1<<i))&((-1)<<i);return;}
}
int main()
{
	int n=read(),i;
	for(i=1;i<n;++i)ins(read(),read());
	dfs(1,0);
	printf("%d",cal(f[1]));
}

Submission Info

Judge Result