hdu 5438 Ponds dfs

  1 #include<cstdio>
  2 #include<cstring>
  3 #include<algorithm>
  4 
  5 using namespace std;
  6 
  7 #define ll long long
  8 #define push_back pb
  9 
 10 const int maxp=1e4+5;
 11 const int maxm=1e5+5;
 12 
 13 struct Edge
 14 {
 15     int to,next;
 16 };
 17 Edge edge[maxm<<1];
 18 
 19 int head[maxp];
 20 int tot;
 21 bool vis[maxp];
 22 int in[maxp];
 23 ll v[maxp];
 24 
 25 void addedge(int u,int v)
 26 {
 27     edge[tot].to=v;
 28     edge[tot].next=head[u];
 29     head[u]=tot++;
 30 }
 31 
 32 ll solve(int ,int );
 33 void dfs(int );
 34 void dfs1(int ,int &,ll &);
 35 
 36 int main()
 37 {
 38     int test;
 39     scanf("%d",&test);
 40     while(test--){
 41         tot=0;
 42         memset(head,-1,sizeof head);
 43         memset(in,0,sizeof in);
 44 
 45         int p,m;
 46         scanf("%d %d",&p,&m);
 47         for(int i=1;i<=p;i++)
 48             scanf("%I64d",&v[i]);
 49         int u,v;
 50         for(int i=0;i<m;i++){
 51             scanf("%d %d",&u,&v);
 52             addedge(u,v);
 53             addedge(v,u);
 54             in[u]++;
 55             in[v]++;
 56         }
 57 
 58         printf("%I64d\n",solve(p,m));
 59     }
 60     return 0;
 61 }
 62 
 63 ll solve(int p,int m)
 64 {
 65     memset(vis,false,sizeof vis);
 66 
 67     for(int i=1;i<=p;i++){
 68         if(!vis[i]&&in[i]<2){
 69             in[i]--;
 70             dfs(i);
 71         }
 72     }
 73 
 74     ll ret=0;
 75     memset(vis,false,sizeof vis);
 76     int num;
 77     ll sum;
 78     for(int i=1;i<=p;i++){
 79         if(!vis[i]&&in[i]>1){
 80             num=0;
 81             sum=0;
 82             dfs1(i,num,sum);
 83             if(num%2)
 84                 ret+=sum;
 85         }
 86     }
 87     return ret;
 88 }
 89 
 90 void dfs(int u)
 91 {
 92     vis[u]=true;
 93     for(int i=head[u];~i;i=edge[i].next){
 94         int v=edge[i].to;
 95         if(vis[v])
 96             continue;
 97         in[v]--;
 98         if(in[v]<2){
 99             in[v]--;
100             dfs(v);
101         }
102     }
103 }
104 
105 void dfs1(int u,int &num,ll &sum)
106 {
107     vis[u]=true;
108     num++;
109     sum+=v[u];
110     for(int i=head[u];~i;i=edge[i].next){
111         int v=edge[i].to;
112         if(vis[v]||in[v]<2)
113             continue;
114         dfs1(v,num,sum);
115     }
116 }