BZOJ 2152 & 点分治

Description:

　　只是打法法塔前测试一下板子

Code:

　　

/*=================================
# Created time: 2016-04-20 14:35
# Filename: 2152.cpp
# Description: 
=================================*/
#define me AcrossTheSky&HalfSummer11  
#include <cstdio>  
#include <cmath>  
#include <ctime>  
#include <string>  
#include <cstring>  
#include <cstdlib>  
#include <iostream>  
#include <algorithm>  
  
#include <set> 
#include <stack>  
#include <queue>  
#include <vector>  
  
#define lowbit(x) (x)&(-x)  
#define Abs(x) ((x) > 0 ? (x) : (-(x)))  
#define FOR(i,a,b) for((i)=(a);(i)<=(b);(i)++)  
#define FORP(i,a,b) for(int i=(a);i<=(b);i++)  
#define FORM(i,a,b) for(int i=(a);i>=(b);i--)  
#define ls(a,b) (((a)+(b)) << 1)  
#define rs(a,b) (((a)+(b)) >> 1)  
#define getlc(a) ch[(a)][0]  
#define getrc(a) ch[(a)][1]  
  
#define maxn 100005 
#define maxm 100005 
#define INF 1070000000  
using namespace std;  
typedef long long ll;  
typedef unsigned long long ull;  
  
template<class T> inline  
void read(T& num){  
    num = 0; bool f = true;char ch = getchar();  
    while(ch < '0' || ch > '9') { if(ch == '-') f = false;ch = getchar();}  
    while(ch >= '0' && ch <= '9') {num = num * 10 + ch - '0';ch = getchar();}  
    num = f ? num: -num;  
} 
int outs[100]; 
template<class T> inline 
void write(T x){ 
	if (x==0) {putchar('0'); putchar(' '); return;} 
	if (x<0) {putchar('-'); x=-x;} 
	int num=0; 
	while (x){ outs[num++]=(x%10); x=x/10;} 
	FORM(i,num-1,0) putchar(outs[i]+'0');
} 
/*==================split line==================*/ 
int n,m,mn,root,cnt,ans,sume=0;
bool vis[maxn];
struct Edge{int to,next,w;} e[maxm];
int first[maxn],sz[maxn],dep[maxn],d[maxn];
inline int gcd(int a,int b) { return b==0?a:gcd(b,a%b);}
inline void addedge(int x,int y,int w){
	sume++; e[sume].to=y; e[sume].w=w;e[sume].next=first[x]; first[x]=sume;
}
inline int getroot(int x,int fa,int sum){
	sz[x]=1; int mx=0,y; //`vis[x]=true;
	for (int i = first[x];i;i=e[i].next)
	if (!vis[y=e[i].to] && e[i].to!=fa){
		getroot(y,x,sum);
		sz[x]+=sz[y];
		mx=max(mx,sz[y]);
	}
	mx=max(mx,sum-mx);
	if (mx<mn) mn=mx,root=x;
}
inline void getdep(int x,int fa){
	dep[++cnt]=d[x]; int y;
	for (int i=first[x];i;i=e[i].next)
		if (!vis[y=e[i].to] && e[i].to!=fa){
			d[y]=d[x]+e[i].w;
			getdep(y,x);
		}
}
inline int cal(int x,int last=0){
	int c[3]; memset(c,0,sizeof(c));
	cnt=0; d[x]=last;
	getdep(x,-1);
	FORP(i,1,cnt) c[dep[i]%3]++;
	return c[0]*c[0]+(c[1]*c[2])*2;
}
inline void dfs(int x,int sum){
	vis[x]=true;
	ans+=cal(x); int y;
	for (int i=first[x];i;i=e[i].next) if (!vis[y=e[i].to]){
		ans-=cal(y,e[i].w);
		int s=sz[y]>sz[x]?sum-sz[x]:sz[y];
		root=0; mn=INF; getroot(y,x,s);
		dfs(root,s);
	}
}
int main(){
	read(n); 
	FORP(i,1,n-1) {
		int x,y,z; read(x); read(y); read(z);
		addedge(x,y,z%3); addedge(y,x,z%3);
	}
	memset(vis,false,sizeof(vis));
	mn=INF;
	getroot((n+1)>>1,-1,n);
	dfs(root,n);
	int down=n*n,t=gcd(ans,down);
	write(ans/t); putchar('/'); write(down/t); puts("");
}