題目地址
題意:定義每條邊的價值爲邊上不同顏色的個數,求整棵樹的價值。
題解:這裏寫鏈接內容
代碼:
#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<vector>
#include<queue>
#include<set>
#include<algorithm>
#include<map>
using namespace std;
typedef long long int ll;
typedef pair<int,int>pa;
const int N=1e6+10;
const int mod=1e9+7;
const ll INF=1e18;
const int inf=1e4;
int read()
{
int x=0;
char ch = getchar();
while('0'>ch||ch>'9')ch=getchar();
while('0'<=ch&&ch<='9')
{
x=(x<<3)+(x<<1)+ch-'0';
ch=getchar();
}
return x;
}
/***********************************************************/
struct node
{
int to,next;
}edge[N<<2];
int head[N<<2];
int n,cas,num,cnt;
ll ans;
ll sum[N],size[N];
int vis[N],col[N];
void init()
{
num=0;
ans=0;
cnt=0;
memset(head,-1,sizeof(head));
memset(vis,0,sizeof(vis));
memset(sum,0,sizeof(sum));
}
void add(int f,int to)
{
edge[cnt].to=to;
edge[cnt].next=head[f];
head[f]=cnt++;
}
void dfs(int x,int y)
{
size[x]=1;
sum[col[x]]++;
ll pre=sum[col[x]];
for(int i=head[x];i!=-1;i=edge[i].next)
{
int v=edge[i].to;
if(v==y) continue;
dfs(v,x);
size[x]+=size[v];
ll conut=size[v]-(sum[col[x]]-pre);
ans+=conut*(conut-1)/2;
sum[col[x]]+=conut;
pre=sum[col[x]];
}
}
int main()
{
cas=1;
while(~scanf("%d",&n))
{
init();
for(int i=1;i<=n;i++)
{
scanf("%d",&col[i]);
if(vis[col[i]]==0)
{
num++;
vis[col[i]]=1;
}
}
for(int i=1;i<n;i++)
{
int u,v;
scanf("%d%d",&u,&v);
add(u,v);
add(v,u);
}
dfs(1,0);
ll op=1ll*num*((ll)n*(n-1)/2);
for(int i=1;i<=n;i++)
{
if(vis[i])
{
ll ct=n-sum[i];
ans+=ct*(ct-1)/2;
}
}
printf("Case #%d: %lld\n", cas++, op-ans);
}
return 0;
}