HDU 1224 无环有向最长路

用bellman_ford的方法，将中间不断取较小值，修改为取较大值就可以了

 

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <iostream>

 4 using namespace std;

 5 const int N = 105;

 6 int dp[N] , k , first[N] , val[N] , x , y , fa[N] , rec[N];

 7 

 8 struct Edge{

 9     int x , y , next , d;

10 }e[N*N];

11 

12 void add_edge(int x , int y , int d)

13 {

14     e[k].x = x , e[k].y = y , e[k].next = first[x] , e[k].d = d;

15     first[x] = k++;

16 }

17 

18 int main()

19 {

20     int T , n , cas = 0;

21     scanf("%d" , &T);

22     while(T--){

23         scanf("%d" , &n);

24         for(int i = 1 ; i<=n ; i++)

25             scanf("%d" , val+i);

26         val[n+1] = 0;

27 

28         int m;

29         scanf("%d" , &m);

30         k=0;

31         for(int i = 0 ; i<m ; i++){

32             scanf("%d%d" , &x , &y);

33             add_edge(x , y , val[y]);

34         }

35 

36         memset(dp , 0 , sizeof(dp));

37         memset(fa , 0 , sizeof(fa));

38         for(int i = 1 ; i<=n ; i++){

39             for(int j = 0 ; j<k ; j++){

40                 int u = e[j].x , v = e[j].y;

41                 if(dp[v] < dp[u] + e[j].d){

42                     dp[v] = dp[u] + e[j].d;

43                     fa[v] = u;

44                    // cout<<"here: "<<u<<" "<<v<<" "<<fa[v]<<" "<<dp[v]<<endl;

45                 }

46             }

47         }

48 

49         printf("CASE %d#\npoints : %d\ncircuit : " , ++cas , dp[n+1]);

50         int cnt = 0 , la = n+1;

51         rec[cnt++] = 1;

52         while(fa[la]){

53             rec[cnt++] = fa[la];

54             la = fa[la];

55         }

56         for(int i = cnt-1 ; i>=1 ; i--)

57             printf("%d->" , rec[i]);

58         printf("%d\n" , rec[0]);

59         if(T>0) puts("");

60     }

61     return 0;

62 }