hdu4280 Island Transport (最大流ISAP算法)

#include <stdio.h>#include <string.h>#define MAXN 100002#define MAXE 400002#define INF 0x3f3f3f3fstruct node{int from,to,next;int cap;}edge[MAXE];int n,m,tot,src,dest,Queue[MAXN],cur[MAXN],Stack[MAXN];;int head[MAXN],level[MAXN],gap[MAXN];//gap[x]=y :说明残留网络中level[i]==x的个数为yvoid addEdge(int u,int v,int w){edge[tot].from=u;edge[tot].to=v;edge[tot].cap=w;edge[tot].next=head[u];head[u]=tot++;edge[tot].from=v;edge[tot].to=u;edge[tot].cap=0;edge[tot].next=head[v];head[v]=tot++;}void BFS(){int front,rear,i,u,v;memset(level,-1,sizeof(level));memset(gap,0,sizeof(gap));gap[0]=1;//说明此时有1个level[i] = 0front=rear=0;level[dest]=0;Queue[rear++]=dest;while(front<rear){u=Queue[front++];for(i=head[u];i!=-1;i=edge[i].next){v=edge[i].to;if(level[v]!=-1||edge[i].cap!=0)continue;Queue[rear++]=v;level[v]=level[u]+1;++gap[level[v]];}}}int SAP(){int maxflow=0,i=0,u,top=0;BFS();memcpy(cur,head,sizeof(head));u=src;while(level[src]<n){if(u==dest){int inser,temp=INF;for(i=0;i!=top;++i){if(temp>edge[Stack[i]].cap){temp=edge[Stack[i]].cap;inser=i;}}for(i=0;i!=top;++i){edge[Stack[i]].cap-=temp;edge[Stack[i]^1].cap+=temp;}maxflow+=temp;top=inser;u=edge[Stack[top]].from;}if(u!=dest&&gap[level[u]-1]==0)break;//出现断层，无增广路for(i=cur[u];i!=-1;i=edge[i].next){//遍历与u相连的未遍历结点if(edge[i].cap!=0&&level[u]==level[edge[i].to]+1)//层序关系， 找到允许break;}if(i!=-1)//找到允许弧{cur[u]=i;Stack[top++]=i;//加入路径栈u=edge[i].to;//查找下一个结点}else//无允许的路径，修改标号 当前点的标号比与之相连的点中最小的多1{int mixn=n;for(i=head[u];i!=-1;i=edge[i].next){//找到与u相连的v中level[v]最小的点if(edge[i].cap==0)continue;if(mixn>level[edge[i].to]){mixn=level[edge[i].to];cur[u]=i;//最小标号就是最新的允许弧}}--gap[level[u]];level[u]=mixn+1;++gap[level[u]];if(u!=src)u=edge[Stack[--top]].from;}}return maxflow;}int main(){int test,ans,i,m,x,y,w;int minx,maxx;scanf("%d",&test);while(test--){minx=INF;maxx=~INF+1;/*n=Scan();m=Scan();*/scanf("%d %d",&n,&m);for(i=1;i<=n;++i){/*x=Scan();y=Scan();*/scanf("%d %d",&x,&y);if(minx>=x){minx=x;src=i;}if(maxx<=x){maxx=x;dest=i;}}tot=0;memset(head,-1,sizeof(head));while(m--){/*x=Scan();y=Scan();w=Scan();*/scanf("%d %d %d",&x,&y,&w);addEdge(x,y,w);addEdge(y,x,w);}ans=SAP();printf("%d\n",ans);}return 0;}