BZOJ3396: [Usaco2009 Jan]Total flow 水流

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cmath>
 4 #include<cstring>
 5 #include<algorithm>
 6 #include<iostream>
 7 #include<vector>
 8 #include<map>
 9 #include<set>
10 #include<queue>
11 #include<string>
12 #define inf 1000000000
13 #define maxn 200
14 #define maxm 1500
15 #define eps 1e-10
16 #define ll long long
17 #define pa pair<int,int>
18 #define for0(i,n) for(int i=0;i<=(n);i++)
19 #define for1(i,n) for(int i=1;i<=(n);i++)
20 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
21 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
22 #define mod 1000000007
23 using namespace std;
24 inline int read()
25 {
26     int x=0,f=1;char ch=getchar();
27     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
28     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
29     return x*f;
30 }
31 int  n,m,s,t,maxflow,tot=1,head[maxn],cur[maxn],h[maxn],q[maxn];
32 struct edge{int go,next,v;}e[maxm];
33 void ins(int x,int y,int z){e[++tot].go=y;e[tot].v=z;e[tot].next=head[x];head[x]=tot;}
34 void insert(int x,int y,int z){ins(x,y,z);ins(y,x,0);}
35 bool bfs()
36 {
37     for(int i=1;i<=150;i++)h[i]=-1;
38     int l=0,r=1;q[1]=s;h[s]=0;
39     while(l<r)
40     {
41         int x=q[++l];
42         for(int i=head[x];i;i=e[i].next)
43          if(e[i].v&&h[e[i].go]==-1)
44          {
45             h[e[i].go]=h[x]+1;q[++r]=e[i].go;
46          }
47     }
48     return h[t]!=-1;
49 }
50 int dfs(int x,int f)
51 {
52     if(x==t) return f;
53     int tmp,used=0;
54     for(int i=head[x];i;i=e[i].next)
55      if(e[i].v&&h[e[i].go]==h[x]+1)
56     {
57         tmp=dfs(e[i].go,min(e[i].v,f-used));
58         e[i].v-=tmp;if(e[i].v)cur[x]=i;
59         e[i^1].v+=tmp;used+=tmp;
60         if(used==f)return f;       
61     }
62     if(!used) h[x]=-1;
63     return used;
64 }
65 void dinic()
66 {
67     maxflow=0;
68     while(bfs())
69     {
70         for (int i=s;i<=t;i++)cur[i]=head[i];maxflow+=dfs(s,inf);
71     }
72 }
73 inline int get()
74 {
75     char ch=‘ ‘;
76     while((ch<‘a‘||ch>‘z‘)&&(ch<‘A‘||ch>‘Z‘))ch=getchar();
77     return ch;
78 }
79 int main()
80 {
81     freopen("input.txt","r",stdin);
82     freopen("output.txt","w",stdout);
83     n=read();
84     for1(i,n)
85      {
86          int x=get(),y=get(),z=read();
87          insert(x,y,z);
88      }
89     s=(int)‘A‘;t=(int)‘Z‘;
90     dinic();
91     printf("%d\n",maxflow);
92     return 0;
93 }