101 lines
2.2 KiB
C++
101 lines
2.2 KiB
C++
#include<stdio.h>
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#include<string.h>
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#include<stack>
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#include<math.h>
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using namespace std;
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#define N 10005
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#define M 20005
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struct node{
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int from,to,next;
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}edge[2*M],edge1[2*M];
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int head[N],tol,n,m,cnt,dfn[N],low[N],visit[N],Belong[N],tol1,head1[N],val[N],val1[N],SUM,Min,count;
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stack<int>S;
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void add(int a,int b)
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{
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edge[tol].from=a;edge[tol].to=b;edge[tol].next=head[a];head[a]=tol++;
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}
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void add1(int a,int b)
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{
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edge1[tol1].from=a;edge1[tol1].to=b;edge1[tol1].next=head1[a];head1[a]=tol1++;
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}
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int min(int a,int b)
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{
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return a<b?a:b;
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}
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void tarjan(int u,int father)
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{
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int j,v,flag;
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dfn[u]=low[u]=cnt++;
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visit[u]=1;
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S.push(u);
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flag=0;
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for(j=head[u];j!=-1;j=edge[j].next)
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{
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v=edge[j].to;
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if(v==father && !flag) {flag=1;continue;}
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if(!visit[v]) tarjan(v,u);
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low[u]=min(low[u],low[v]);
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}
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if(dfn[u]==low[u])
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{
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count++;
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do{
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v=S.top();
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S.pop();
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Belong[v]=count;
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val[count]+=val1[v];
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}while(v!=u);
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}
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}
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int dfs(int u,int father)
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{
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int j,v,sum;
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sum=val[u];
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for(j=head1[u];j!=-1;j=edge1[j].next)
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{
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v=edge1[j].to;
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if(v==father) continue;
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sum+=dfs(v,u);
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}
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Min=min(Min,abs(SUM-2*sum));
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return sum;
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}
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int main()
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{
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int i,a,b;
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while(scanf("%d%d",&n,&m)!=EOF)
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{
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memset(head,-1,sizeof(head));
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tol=cnt=0;
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SUM=0;
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for(i=0;i<n;i++)
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{
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scanf("%d",&val1[i]);
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SUM+=val1[i];
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}
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for(i=1;i<=m;i++)
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{
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scanf("%d%d",&a,&b);
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add(a,b);
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add(b,a);
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}
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memset(visit,0,sizeof(visit));
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memset(val,0,sizeof(val));
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count=0;
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tarjan(0,0);
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if(count==1) {printf("impossible\n");continue;}
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tol1=0;
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memset(head1,-1,sizeof(head1));
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for(i=0;i<tol;i++)
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{
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a=edge[i].from;
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b=edge[i].to;
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if(Belong[a]!=Belong[b]) add1(Belong[a],Belong[b]);
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}
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Min=0xfffffff;
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dfs(1,0);
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printf("%d\n",Min);
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}
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return 0;
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}
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