POJ 1459 Power Network(最大流）

题目链接

算是一个模版题把。构造一个源点和汇点，所有的核电站都是从源点出发的，所有的用户都汇集到汇点，跑一次最大流就可以了。模版敲的不是很熟。

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <queue>

 4 using namespace std;

 5 const int INF = 0xffffff;

 6 int flow[201][201],low[201],path[201];

 7 int str,end,n;

 8 int bfs()

 9 {

10     int t,i;

11     queue<int> que;

12     memset(path,-1,sizeof(path));

13     que.push(str);

14     low[str] = INF;

15     while(!que.empty())

16     {

17         t = que.front();

18         que.pop();

19         if(t == end) break;

20         for(i = 0; i <= n+1; i ++)

21         {

22             if(i != str&&path[i] == -1&&flow[t][i])

23             {

24                 path[i] = t;

25                 low[i] = low[t] < flow[t][i] ? low[t]:flow[t][i];

26                 que.push(i);

27             }

28         }

29     }

30     if(path[end] == -1)

31         return -1;

32     else

33         return low[end];

34 }

35 int EK()

36 {

37     int ans = 0,now,res;

38     while((res = bfs()) != -1)

39     {

40         ans += res;

41         now = end;

42         while(now != str)

43         {

44             flow[path[now]][now] -= res;

45             flow[now][path[now]] += res;

46             now = path[now];

47         }

48     }

49     return ans;

50 }

51 inline void clean()

52 {

53     char ch;

54     for(;;)

55     {

56         scanf("%c",&ch);

57         if(ch == '(') break;

58     }

59 }

60 int main()

61 {

62     int i,m,sv,ev,w,np,nc;

63     while(scanf("%d%d%d%d%*c",&n,&np,&nc,&m)!=EOF)

64     {

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

66         for(i = 1; i <= m; i ++)

67         {

68             clean();

69             scanf("%d,%d)%d",&sv,&ev,&w);

70             flow[sv][ev] += w;

71         }

72         for(i = 1; i <= np; i ++)

73         {

74             clean();

75             scanf("%d)%d",&ev,&w);

76             flow[n][ev] += w;

77         }

78         for(i = 1; i <= nc; i ++)

79         {

80             clean();

81             scanf("%d)%d%*c",&sv,&w);

82             flow[sv][n+1] += w;

83         }

84         str = n;

85         end = n+1;

86         printf("%d\n",EK());

87     }

88     return 0;

89 }