codevs 1993草地排水 isap模板题

Posted 2020-06-14

高天宇的isap模板，不用解释了吧。。。

#include<queue>
#include<cstdio>
#include<cctype>
#include<cstring>
#include<algorithm>
using namespace std;
const int inf=1E9;
int N,M,point[203],nxt[403],v[403],c[403],cnt=0;
int deep[203],num[203],cur[203],lastedge[203];
bool vis[203];
inline int getint(){char c;while (!isdigit(c=getchar()));int a=c-‘0‘;while (isdigit(c=getchar())) a=a*10+c-‘0‘;return a;}
inline void insect(int x,int y,int z){nxt[cnt]=point[x];point[x]=cnt;v[cnt]=y;c[cnt]=z;cnt++;}
inline void bfs(int t){
    for (int i=1;i<=N;++i) deep[i]=N;
    memset(vis,0,sizeof(vis));
    queue<int>q; vis[t]=1; q.push(t); deep[t]=0;
    while (!q.empty()){
        int now=q.front(); q.pop();
        for (int tmp=point[now];tmp!=-1;tmp=nxt[tmp])
         if ((vis[v[tmp]]==0)&&(c[tmp^1]!=0)){
             vis[v[tmp]]=1;
             q.push(v[tmp]);
             deep[v[tmp]]=deep[now]+1;
         }
    }
}
inline int addflow(int s,int t){
    int ans=inf,now=t;
    while (now!=s){
        ans=min(ans,c[lastedge[now]]);
        now=v[lastedge[now]^1];
    }now=t;
    while (now!=s){
        c[lastedge[now]]-=ans;
        c[lastedge[now]^1]+=ans;
        now=v[lastedge[now]^1];
    }return ans;
}
inline int isap(int s,int t){
    int ans=0,now=s; bfs(t);
    for (int i=1;i<=N;++i) num[deep[i]]++,cur[i]=point[i];
    while (deep[s]<N){
        if (now==t){
            ans+=addflow(s,t);
            now=s;
        }bool has_find=0;
        for (int tmp=cur[now];tmp!=-1;tmp=nxt[tmp]){
            int u=v[tmp];
            if ((deep[u]+1==deep[now])&&(c[tmp]!=0)){
                has_find=1;
                cur[now]=tmp;
                lastedge[u]=tmp;
                now=u;
                break; 
            }
        }
        if (has_find==0){
            int minn=N-1;
            for (int tmp=point[now];tmp!=-1;tmp=nxt[tmp])
             if (c[tmp]!=0) minn=min(minn,deep[v[tmp]]);
            if (--num[deep[now]]==0) break;
            num[deep[now]=minn+1]++;
            cur[now]=point[now];
            if (now!=s) now=v[lastedge[now]^1];
        }
    }return ans;
}
int main(){
    memset(point,-1,sizeof(point));
    memset(nxt,-1,sizeof(nxt));
    M=getint();N=getint();
    for (int i=1;i<=M;++i){
        int x=getint(),y=getint(),z=getint();
        insect(x,y,z); insect(y,x,0);
    }printf("%d\n",isap(1,N));return 0;
}