hdu1532 Drainage Ditches（最大流）

Posted 2021-01-02 scott527407973

http://acm.hdu.edu.cn/showproblem.php?pid=1532

代码来自https://blog.csdn.net/qq_31759205/article/details/52947859

直接套最大流模板

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int inf=0x3f3f3f3f;
 4 const int maxn=205;
 5 const int maxe=4*maxn*maxn;
 6 struct MaxFlow
 7 {
 8     struct Edge
 9     {
10         int next,to,w;
11     }edge[maxe];
12     int head[maxn],tot,level[maxn];
13     void init()
14     {
15         memset(head,-1,sizeof(head));
16         tot=0;
17     }
18     void add(int u,int v,int w)
19     {
20         edge[tot].to=v;
21         edge[tot].w=w;
22         edge[tot].next=head[u];
23         head[u]=tot++;
24 
25         edge[tot].to=u;
26         edge[tot].w=0;
27         edge[tot].next=head[v];
28         head[v]=tot++;
29     }
30     bool bfs(int s,int t)
31     {
32         memset(level,-1,sizeof(level));
33         queue<int>q;
34         q.push(s);
35         level[s]=0;
36         while(!q.empty())
37         {
38             int u=q.front();q.pop();
39             for(int i=head[u];~i;i=edge[i].next)
40             {
41                 int v=edge[i].to;
42                 if(edge[i].w>0&&level[v]<0)
43                 {
44                     level[v]=level[u]+1;
45                     q.push(v);
46                 }
47             }
48         }
49         return level[t]>0;
50     }
51     int dfs(int u,int t,int f)
52     {
53         if(u==t)    return f;
54         for(int i=head[u];~i;i=edge[i].next)
55         {
56             int v=edge[i].to;
57             if(edge[i].w>0&&level[v]>level[u])
58             {
59                 int d=dfs(v,t,min(f,edge[i].w));
60                 if(d>0)
61                 {
62                     edge[i].w-=d;
63                     edge[i^1].w+=d;
64                     return d;
65                 }
66             }
67         }
68         level[u]=-1;
69         return 0;
70     }
71     int slove(int s,int t)
72     {
73         int flow=0,f;
74         while(bfs(s,t))
75         {
76             while(f=dfs(s,t,inf))   flow+=f;
77         }
78         return flow;
79     }
80 }F;
81 int main()
82 {
83     int n,m;
84     while(~scanf("%d%d",&m,&n))
85     {
86         F.init();
87         for(int i=0;i<m;i++)
88         {
89             int u,v,c;
90             scanf("%d%d%d",&u,&v,&c);
91             F.add(u,v,c);
92         }
93         printf("%d
",F.slove(1,n));
94     }
95     return 0;
96 }

View Code