HDU 1532 Drainage Ditches 最大流 （Edmonds_Karp）

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

感觉题意不清楚，不知道是不是个人英语水平问题。本来还以为需要维护入度和出度来找源点和汇点呢，看讨论才知道1就是起点，m就是汇点。。好想把代码写的工程化一点。

 1 #include <stdio.h>

 2 #include <string.h>

 3 #include <queue>

 4 #include <algorithm>

 5 using namespace std;

 6 

 7 const int INF = 0x3f3f3f3f;

 8 int n, m;

 9 int cap[210][210], flow[210][210], res[210], pre[210];

10 queue<int>que;

11 

12 int Edmonds_Karp()

13 {

14     while(!que.empty())

15     {

16         que.pop();

17     }

18     int flow_sum = 0;

19     while(true)

20     {

21         memset(res, 0, sizeof(res));

22         res[1] = INF;

23         que.push(1);

24         while(!que.empty())

25         {

26             int u = que.front();

27             que.pop();

28             for(int v = 1; v <= m; v++)

29             {

30                 if(!res[v] && cap[u][v] > flow[u][v])

31                 {

32                     pre[v] = u;

33                     que.push(v);

34                     res[v] = min(res[u], cap[u][v] - flow[u][v]);

35                 }

36             }

37         }

38         if(res[m] == 0)break;

39         for(int u = m; u != 1; u = pre[u])

40         {

41             flow[pre[u]][u] += res[m];

42             flow[u][pre[u]] -= res[m];

43         }

44         flow_sum += res[m];

45     }

46     return flow_sum;

47 }

48 

49 int main()

50 {

51     int u, v, w;

52     while(scanf("%d %d", &n, &m) != EOF)

53     {

54         memset(cap, 0, sizeof(cap));

55         memset(flow, 0, sizeof(flow));

56         for(int i = 0; i < n; i++)

57         {

58             scanf("%d %d %d", &u, &v, &w);

59             cap[u][v] += w;

60         }

61         printf("%d\n", Edmonds_Karp());

62     }

63     return 0;

64 }

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