P2936 [USACO09JAN]全流Total Flow

也是模板题

注意：源点为A（1），终点为Z（26）。中间处理 连接边：add(u-'A'+1,v-'A'+1,w); add(v-'A'+1,u-'A'+1,0);

题目链接：https://www.luogu.com.cn/problem/P2936

#include 
using namespace std;
const int maxn=1000000+5;
int to[maxn*2],last[maxn],nxt[maxn*2],wi[maxn*2],deep[maxn],cnt=-1,n,m,s,t;
void add(int u,int v,int w){wi[++cnt]=w; to[cnt]=v; nxt[cnt]=last[u]; last[u]=cnt; return ;}
bool bfs()
{
    queue <int> Q;
    while(!Q.empty())
        Q.pop();
    memset(deep,0,sizeof(deep));
    deep[s]=1;
    Q.push(s);
    do{
        int u=Q.front(); Q.pop();
        for(int i=last[u];i!=-1;i=nxt[i])
            if(wi[i]>0 && deep[to[i]]==0)
            {
                deep[to[i]]=deep[u]+1; 
                Q.push(to[i]);
            }
    }while(!Q.empty());
    if(deep[t]!=0) return 1; 
    return 0;
}
int dfs(int u,int dist)
{
    if(u==t) return dist;
    for(int i=last[u];i!=-1;i=nxt[i])
        if(deep[to[i]]==deep[u]+1 && wi[i]!=0){
            int di=dfs(to[i],min(wi[i],dist));
            if(di>0)
            {
                wi[i]-=di;
                wi[i^1]+=di;
                return di;
            }
        }
    return 0;
}
int dinic()
{
    int ans=0;
    while(bfs())
        while(int d=dfs(s,100000007))
            ans+=d;
    return ans;
}
int main()
{
    memset(nxt,-1,sizeof(nxt));
    memset(last,-1,sizeof(last)); 
    cin>>m;
    s=1,t=26;
    for(int i=1;i<=m;i++)
    {
        char u,v; int w; cin>>u>>v>>w;
        add(u-'A'+1,v-'A'+1,w); add(v-'A'+1,u-'A'+1,0);
    }
    cout<<dinic();
    return 0;
}