Power Network（网络流最大流）

 1 #include<iostream>
 2 #include<stdio.h>
 3 #include<string.h>
 4 using namespace std;
 5 #define MAXN 202
 6 const int INT_MAX = 0x3f3f3f3f ;
 7 int s, t;
 8 int n, np, nc, m;
 9 char str[50];
10 int c[MAXN][MAXN];
11 int f[MAXN][MAXN];
12 int e[MAXN];
13 int h[MAXN];
14 void push(int u, int v)
15 {
16     int d = min(e[u], c[u][v] - f[u][v]);
17     f[u][v] += d;
18     f[v][u] = -f[u][v];
19     e[u] -= d;
20     e[v] += d;
21 }
22 bool relabel(int u)
23 {
24     int mh = INT_MAX;
25     for(int i=0; i<n+2; i++)
26     {
27         if(c[u][i] > f[u][i])
28             mh = min(mh, h[i]);
29     }
30     if(mh == INT_MAX)
31         return false; //残留网络中无从u出发的路
32     h[u] = mh + 1;
33     for(int i=0; i<n+2; i++)
34     {
35         if(e[u] == 0) //已无余流，不需再次push
36             break;
37         if(h[i] == mh && c[u][i] > f[u][i]) //push的条件
38             push(u, i);
39     }
40     return true;
41 }
42 void init_preflow()
43 {
44     memset(h, 0, sizeof(h));
45     memset(e, 0, sizeof(e));
46     h[s] = n+2;
47     for(int i=0; i<n+2; i++)
48     {
49         if(c[s][i] == 0)
50             continue;
51         f[s][i] = c[s][i];
52         f[i][s] = -f[s][i];
53         e[i] = c[s][i];
54         e[s] -= c[s][i];
55     }
56 }
57 void push_relabel()
58 {
59     init_preflow();
60     bool flag = true; //表示是否还有relabel操作
61     while(flag)
62     {
63         flag = false;
64         for(int i=0; i<n; i++)
65             if(e[i] > 0)
66                 flag = flag || relabel(i);
67     }
68 }
69 int main()
70 {
71     while(scanf("%d%d%d%d", &n, &np, &nc, &m) != EOF)
72     {
73         s = n; t = n+1;
74         memset(c, 0, sizeof(c));
75         memset(f, 0, sizeof(f));
76         while(m--)
77         {
78             scanf("%s", &str);
79             int u=0, v=0, z=0;
80             sscanf(str, "(%d,%d)%d", &u, &v, &z);
81             c[u][v] = z;
82         }
83         for(int i=0; i<np+nc; i++)
84         {
85             scanf("%s", &str);
86             int u=0, z=0;
87             sscanf(str, "(%d)%d", &u, &z);
88             if(i < np)
89                 c[s][u] = z;
90             else if(i >= np && i < np + nc)
91                 c[u][t] = z;
92         }
93         push_relabel();
94         printf("%d\n", e[t]);
95     }
96 }