hdu5438 Ponds

Time Limit: 1500/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)

Total Submission(s): 2677    Accepted Submission(s): 850

Problem Description

Betty owns a lot of ponds, some of them are connected with other ponds by pipes, and there will not be more than one pipe between two ponds. Each pond has a value v.

Now Betty wants to remove some ponds because she does not have enough money. But each time when she removes a pond, she can only remove the ponds which are connected with less than two ponds, or the pond will explode.

Note that Betty should keep removing ponds until no more ponds can be removed. After that, please help her calculate the sum of the value for each connected component consisting of a odd number of ponds

 

Input

The first line of input will contain a number T(1≤T≤30) which
is the number of test cases.

For each test case, the first line contains two number separated by a blank. One is the number p(1≤p≤104) which
represents the number of ponds she owns, and the other is the number m(1≤m≤105) which
represents the number of pipes.

The next line contains p numbers v1,...,vp,
where vi(1≤vi≤108) indicating
the value of pond i.

Each of the last m lines
contain two numbers a and b,
which indicates that pond a and
pond b are
connected by a pipe.

 

Output

For each test case, output the sum of the value of all connected components consisting of odd number of ponds after removing all the ponds connected with less than two pipes.

 

Sample Input

1
7 7
1 2 3 4 5 6 7
1 4
1 5
4 5
2 3
2 6
3 6
2 7

 

Sample Output

21

 

这题可以用拓扑排序做，先删除所有能删除的点，然后再一遍dfs就行了。

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<string>
#include<algorithm>
using namespace std;
typedef long long ll;
#define inf 99999999
#define pi acos(-1.0)
#define maxn 10040
int value[maxn],du[maxn],vis[maxn],n;
ll sum1,num1;

struct edge{
    int to,next,len;
}e[200050];
int first[maxn];
int q[1111111];

void topu()
{
    int i,j,front,rear,x,xx,v;
    front=1;rear=0;
    for(i=1;i<=n;i++){
        if(du[i]<=1){
            rear++;q[rear]=i;
            vis[i]=1;
        }
    }
    while(front<=rear){
        x=q[front];
        front++;
        for(i=first[x];i!=-1;i=e[i].next){
            v=e[i].to;
            if(vis[v])continue;
            du[v]--;
            if(du[v]<=1){
                rear++;
                q[rear]=v;
                vis[v]=1;
            }
        }
    }
}

void dfs(int root)
{
    int i,j,v;
    vis[root]=1;
    num1++;
    sum1+=value[root];
    for(i=first[root];i!=-1;i=e[i].next){
        v=e[i].to;
        if(!vis[v]){
            dfs(v);
        }
    }
}

int main()
{
    int m,i,j,T,tot,c,d;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        for(i=1;i<=n;i++){
            scanf("%d",&value[i]);
        }
        tot=0;
        memset(first,-1,sizeof(first));
        memset(du,0,sizeof(du));
        memset(vis,0,sizeof(vis));
        for(i=1;i<=m;i++){
            scanf("%d%d",&c,&d);
            du[c]++;
            du[d]++;
            tot++;
            e[tot].next=first[c];e[tot].to=d;
            first[c]=tot;

            tot++;
            e[tot].next=first[d];e[tot].to=c;
            first[d]=tot;

        }
        topu();
        ll sum=0;
        for(i=1;i<=n;i++){
            if(vis[i])continue;
            sum1=0;
            num1=0;
            dfs(i);
            if(num1&1)sum+=sum1;
        }
        printf("%lld\n",sum);
    }
    return 0;
}