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

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int N = 105;
int dp[N] , k , first[N] , val[N] , x , y , fa[N] , rec[N];

struct Edge{
    int x , y , next , d;
}e[N*N];

void add_edge(int x , int y , int d)
{
    e[k].x = x , e[k].y = y , e[k].next = first[x] , e[k].d = d;
    first[x] = k++;
}

int main()
{
    int T , n , cas = 0;
    scanf("%d" , &T);
    while(T--){
        scanf("%d" , &n);
        for(int i = 1 ; i<=n ; i++)
            scanf("%d" , val+i);
        val[n+1] = 0;

        int m;
        scanf("%d" , &m);
        k=0;
        for(int i = 0 ; i<m ; i++){
            scanf("%d%d" , &x , &y);
            add_edge(x , y , val[y]);
        }

        memset(dp , 0 , sizeof(dp));
        memset(fa , 0 , sizeof(fa));
        for(int i = 1 ; i<=n ; i++){
            for(int j = 0 ; j<k ; j++){
                int u = e[j].x , v = e[j].y;
                if(dp[v] < dp[u] + e[j].d){
                    dp[v] = dp[u] + e[j].d;
                    fa[v] = u;
                   // cout<<"here: "<<u<<" "<<v<<" "<<fa[v]<<" "<<dp[v]<<endl;
                }
            }
        }

        printf("CASE %d#
points : %d
circuit : " , ++cas , dp[n+1]);
        int cnt = 0 , la = n+1;
        rec[cnt++] = 1;
        while(fa[la]){
            rec[cnt++] = fa[la];
            la = fa[la];
        }
        for(int i = cnt-1 ; i>=1 ; i--)
            printf("%d->" , rec[i]);
        printf("%d
" , rec[0]);
        if(T>0) puts("");
    }
    return 0;
}