hdu 5438 Ponds DFS

#include<bits/stdc++.h>
using namespace std;
const int N=10000+5;
typedef long long ll;
struct Edge
{
    int u,v,use;
};
vector<Edge>edge;
vector<int>g[N];
int n,m,a[N],in[N],cnt;
ll sum;

void Addedge(int u,int v)
{
    in[v]++;in[u]++;
    Edge tp;
    tp.u=u;tp.v=v;tp.use=1;
    edge.push_back(tp);
    g[u].push_back(edge.size()-1);
    g[v].push_back(edge.size()-1);
}

int dfs(int u)
{
    int i,v;
    in[u]=0;
    sum+=a[u];
    cnt++;
    for(i=0; i<g[u].size(); i++)
    {
        if(edge[g[u][i]].use==0) continue;
        else edge[g[u][i]].use=0;
        if(edge[g[u][i]].u==u) v=edge[g[u][i]].v;
        else v=edge[g[u][i]].u;
        if(in[v]==0) continue;
        dfs(v);
    }
}
int main()
{
    int _,u,v,i;
    ll ans;
    scanf("%d",&_);
    while(_--)
    {
        scanf("%d%d",&n,&m);
        edge.clear();
        for(i=0; i<n; i++)
            g[i].clear();
        for(i=0; i<n; i++)
            scanf("%d",&a[i]);
        memset(in,0,sizeof(in));
        for(i=0; i<m; i++)
        {
            scanf("%d%d",&u,&v);
            Addedge(u-1,v-1);
        }
        stack<int>st;
        for(i=0; i<n; i++)
            if(in[i]==1)
                st.push(i);
        while(!st.empty())
        {
            u=st.top();
            in[u]=0;
            st.pop();
            for(i=0; i<g[u].size(); i++)
            {
                if(edge[g[u][i]].use==0) continue;
                else edge[g[u][i]].use=0;
                if(edge[g[u][i]].u==u) v=edge[g[u][i]].v;
                else v=edge[g[u][i]].u;
                //printf("%d
",v);
                in[v]--;
                if(in[v]==1) st.push(v);
            }
        }
        ans=0;
        for(i=0; i<n; i++)
        {
            if(in[i]!=0)
            {
                cnt=0;
                sum=0;
                dfs(i);
                if(cnt%2==1) ans+=sum;
            }
        }
        printf("%lld
",ans);
    }
    return 0;
}