文章标题 HDU 4280 ：Island Transport （最大流--ISAP）

来源：互联网发布：c语言的位域编辑：程序博客网时间：2024/06/02 07:04
题目链接
一开始用的dinic 发现T了，然后换了个IS AP的模板

代码：
#include <iostream>#include <cstdio>#include <cstring>#include <string>#include <queue>#include <set>#include <map>#include <algorithm>#include <math.h>#include <vector>using namespace std;typedef long long ll;const int mod=1e9+7;const int maxn=1e5+10;const int inf=0x3f3f3f3f;const int maxm=1000006;struct Edge{    int to,nex,cap,flow;};struct ISAP{    Edge edge[maxm];    int tol;    int head[maxn];    int gap[maxn],dep[maxn],cur[maxn];    int n,m;    void init() {        tol=0;        memset(head,-1,sizeof(head));    }    void addedge(int u,int v,int w,int rw=0) {        edge[tol].to=v;        edge[tol].cap=w;        edge[tol].flow=0;        edge[tol].nex=head[u];        head[u]=tol++;        edge[tol].to=u;        edge[tol].cap=rw;        edge[tol].flow=0;        edge[tol].nex=head[v];        head[v]=tol++;    }    int Q[maxn];    void BFS(int start,int end) {        memset(dep,-1,sizeof(dep));        memset(gap,0,sizeof(gap));        gap[0]=1;        int front=0, rear=0;        dep[end]=0;        Q[rear++]=end;        while(front!=rear){            int u=Q[front++];            for(int i=head[u];i!=-1;i=edge[i].nex){                int v=edge[i].to;                if(dep[v]!=-1)continue;                Q[rear++]=v;                dep[v]=dep[u]+1;                gap[dep[v]]++;            }        }    }    int S[maxn];    int sap(int start,int end,int n) {        BFS(start,end);        memcpy(cur,head,sizeof(head));        int top=0;        int u=start;        int ans=0;        while(dep[start]<n) {            if(u==end) {                int Min=inf;                int inser;                for(int i=0;i<top;i++)                    if(Min>edge[S[i]].cap-edge[S[i]].flow) {                        Min=edge[S[i]].cap-edge[S[i]].flow;                        inser=i;                    }                for(int i=0;i<top;i++) {                    edge[S[i]].flow+=Min;                    edge[S[i]^1].flow-=Min;                }                ans+=Min;                top=inser;                u=edge[S[top]^1].to;                continue;            }            bool flag=false;            int v;            for(int i=cur[u];i!=-1;i=edge[i].nex) {                v=edge[i].to;                if(edge[i].cap-edge[i].flow&&dep[v]+1==dep[u]) {                    flag=true;                    cur[u]=i;                    break;                }            }            if(flag){                S[top++]=cur[u];                u=v;                continue;            }            int Min=n;            for(int i=head[u];i!=-1;i=edge[i].nex)                if(edge[i].cap-edge[i].flow&&dep[edge[i].to]<Min) {                    Min=dep[edge[i].to];                    cur[u]=i;                }            gap[dep[u]]--;            if(!gap[dep[u]])return ans;            dep[u]=Min+1;            gap[dep[u]]++;            if(u!=start)u=edge[S[--top]^1].to;        }        return ans;    }}isap;int N,M;struct point {    int x,y;}p[maxn];int main(){    int T;    scanf ("%d",&T);    while (T--){        scanf ("%d%d",&N,&M);        isap.init();        for (int i=1;i<=N;i++){            scanf ("%d%d",&p[i].x,&p[i].y);        }        int u,v,c;        for (int i=1;i<=M;i++){            scanf ("%d%d%d",&u,&v,&c);            isap.addedge(u,v,c);            isap.addedge(v,u,c);        }        int st=1,ed=1;        for (int i=2;i<=N;i++){            if (p[st].x>p[i].x)st=i;            if (p[ed].x<p[i].x)ed=i;        }        int ans=isap.sap(st,ed,N);        printf ("%d\n",ans);    }    return 0;}
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