HDU4280 Island Transport

ISAP求最大流模板

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<queue>
using namespace std;
const int maxn=100010;
const int inf=1e9;
struct node {
    int from,to,next;
    int cap;
}edge[maxn*4];
int tol;
int head[maxn];
int dep[maxn];
int gap[maxn];//gep[x]=y说明残量网络中dep[i]==x的个数为y
int n;//点的个数
void init()
{
    tol=0;
    memset(head,-1,sizeof(head));
}

void addedge(int u,int v,int w)
{
    edge[tol].from=u;
    edge[tol].to=v;
    edge[tol].cap=w;
    edge[tol].next=head[u];
    head[u]=tol++;
}
void bfs (int st,int ed) {
    memset (dep,-1,sizeof(dep));
    memset (gap,0,sizeof(gap));
    gap[0]=1;
    queue<int> q;
    dep[ed]=0;
    q.push(ed);
    while (!q.empty()) {
        int u=q.front();
        q.pop();
        for (int i=head[u];i!=-1;i=edge[i].next) {
            int v=edge[i].to;
            if (dep[v]!=-1) continue;
            q.push(v);
            dep[v]=dep[u]+1;
            gap[dep[v]]++;
        }
    }
} 
int sap (int st,int ed) {
    int res=0;
    bfs (st,ed);
    int cur[maxn];
    int s[maxn];
    int top=0;
    memcpy (cur,head,sizeof(head));
    int u=st;
    int i;
    while (dep[st]<n) {
        if (u==ed) {
            int tmp=inf;
            int inser;
            for (i=0;i<top;i++)
            if (tmp>edge[s[i]].cap) {
                tmp=edge[s[i]].cap;
                inser=i;
            }
            for (i=0;i<top;i++) {
                edge[s[i]].cap-=tmp;
                edge[s[i]^1].cap+=tmp;
            }
            res+=tmp;
            top=inser;
            u=edge[s[top]].from;
        }
        if (u!=ed&&gap[dep[u]-1]==0) break;
        for (i=cur[u];i!=-1;i=edge[i].next) 
        if (edge[i].cap!=0&&dep[u]==dep[edge[i].to]+1) break;
        if (i!=-1) {
            cur[u]=i;
            s[top++]=i;
            u=edge[i].to;
        }
        else {
            int min=n;
            for (i=head[u];i!=-1;i=edge[i].next) {
                if (edge[i].cap==0) continue;
                if (min>dep[edge[i].to]) {
                    min=dep[edge[i].to];
                    cur[u]=i;
                }
            }
            gap[dep[u]]--;
            dep[u]=min+1;
            gap[dep[u]]++;
            if (u!=st) u=edge[s[--top]].from;
        }
    }
    return res;
}
int main() {
    int start,end;
    int m;
    int u,v,z;
    int T;
    scanf("%d",&T);
    while(T--) {
        init();
        scanf("%d%d",&n,&m);
        int Min=inf;
        int Max=-inf;
        int x,y;
        for(int i=1;i<=n;i++) {
            scanf("%d%d",&x,&y);
            if(Min>x) {
                Min=x;
                start=i;
            }
            if(Max<x) {
                Max=x;
                end=i;
            }
        }
        while(m--) {
            scanf("%d%d%d",&u,&v,&z);
            addedge(u,v,z);
            addedge(v,u,z);
        }
        //n一定是点的总数，这是使用SAP模板需要注意的
        int ans=sap(start,end);
        printf("%d
",ans);
    }
    return 0;
}