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为什么RE了,求高人指点我用的是二分查找+ISAP求最大流,感觉不会RE啊 #include<iostream> #include<queue> #include<algorithm> using namespace std; const int VMAX=233; int K,C,M,V; int p[3501],l=0; int a[VMAX][VMAX],c[VMAX][VMAX],d[VMAX],pre[VMAX],sumd[VMAX]; void set() { int t=V-1; memset(d,1,sizeof(d)); memset(sumd,0,sizeof(sumd)); queue<int> P; P.push(t); d[t]=0; sumd[0]=1; while(!P.empty()) { int k=P.front(); P.pop(); for(int i=0;i<V;i++) if(c[i][k]&&d[i]>=V) { P.push(i); d[i]=d[k]+1; sumd[d[i]]++; } } } int find(int i) { for(int j=0;j<V;j++) if(c[i][j]&&d[i]==d[j]+1) return j; return -1; } int num(int i) { int t=1000000000; for(int j=0;j<V;j++) if(c[i][j]&&d[j]+1<t) t=d[j]+1; return (t==1000000000)?V:t; } int maxflow(int s,int t)//ISAP { set(); int i=s,sumflow=0; while(d[s]<V) { int k=find(i); if(k>=0) { pre[k]=i; i=k; if(i==t) { int flow=1000000000; for(i=t;i!=s;i=pre[i]) if(flow>c[pre[i]][i]) flow=c[pre[i]][i]; for(i=t;i!=s;i=pre[i]) { c[pre[i]][i]-=flow; c[i][pre[i]]+=flow; } sumflow+=flow; } } else { int x=num(i); if(--sumd[d[i]]==0) break; d[i]=x; sumd[x]++; if(i!=s) i=pre[i]; } } return sumflow; } int check(int x)//构图 { memset(c,0,sizeof(c)); for(int i=0;i<K;i++) for(int j=K;j<K+C;j++) if(a[i][j]<=x) c[i][j]=1; for(int i=0;i<K;i++) c[V-2][i]=M; for(int i=K;i<K+C;i++) c[i][V-1]=1; int o=maxflow(V-2,V-1); if(o>=C) return 1; else return 0; } int main() { cin>>K>>C>>M; V=K+C; for(int i=0;i<V;i++) for(int j=0;j<V;j++) { cin>>a[i][j]; if(a[i][j]==0) a[i][j]=1000000000; } for(int k=0;k<V;k++)//Floyd for(int i=0;i<V;i++) for(int j=0;j<V;j++) if(a[i][k]+a[k][j]<a[i][j]) a[i][j]=a[i][k]+a[k][j]; V+=2; int low,high; for(int i=0;i<K;i++) for(int j=K;j<K+C;j++) { if(a[i][j]>high&&a[i][j]!=1000000000) high=a[i][j]; if(a[i][j]<low) low=a[i][j]; } while(low<=high)//二分查找 { int mid=(low+high)/2; if(check(mid)==1) high=mid-1; else low=mid+1; } cout<<low<<endl; return 0; } Followed by: Post your reply here: |
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