poj 3249 dp

#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>

using namespace std;

const int M = 100005;
const int MAX = 99999999;
int dist[M];
int rdu[M];
int cdu[M];
int value[M];
vector<int>s[M];
int n, m;
int ans;

void work() {


    queue<int>que;
    for(int i = 1; i <= n; i++)
    if(!rdu[i]) {

         que.push(i);
         dist[i] = value[i];
    }
    while(!que.empty()) {

        int v = que.front();
          que.pop();
          for(int i = 0; i < (int)s[v].size(); i++) {

                int k = s[v][i];
                dist[k] = max(dist[k], dist[v] + value[k]);
                rdu[k]--;
                if(!rdu[k])
                    que.push(k);
          }
    }
}

int main()
{
    int a, b;
   while(scanf("%d%d", &n, &m) != EOF) {

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

            scanf("%d", &value[i]);
            s[i].clear();
            dist[i] = -MAX;
            rdu[i] = 0;
            cdu[i] = 0;

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

            scanf("%d%d", &a,&b);
            rdu[b]++;
            cdu[a]++;
            s[a].push_back(b);
        }
        work();
        ans = -MAX;
        for(int i = 1; i <= n; i++) {

            if(!cdu[i])
                ans = max(ans, dist[i]);
        }
        printf("%d\n", ans);
   }
    return 0;
}