POJ 3249 Test for Job（拓扑排序）

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>

using namespace std;
const int N = 100009;
const int M = 1000009;
const int INF = 0x3f3f3f3f;
int n,m;
struct LT{
    int nex,to;
} L[M];
int F
,cnt;
void add(int f,int t)
{
    L[cnt].nex = F[f];
    L[cnt].to = t;
    F[f] =cnt++;
}
int val
;
int in
;
int sum
;
queue<int> que;
void init()
{
    for(int i=1;i<=n;i++) scanf("%d",&val[i]),sum[i]=-INF;
    int f,t;
    memset(F,0,sizeof(F)),cnt=1;
    memset(in,0,sizeof(in));
    for(int i=0;i<m;i++) scanf("%d%d",&f,&t),add(f,t),in[t]++;
}
void solve()
{

    int ans = -INF;
    while(!que.empty()) que.pop();
    for(int i=1;i<=n;i++)
    if(in[i]==0){
         que.push(i),sum[i]=val[i];
         if(F[i]==0) ans=max(ans,sum[i]);///孤立点
         }
    while(!que.empty())
    {
        int e = que.front();que.pop();
        for(int i=F[e];i;i=L[i].nex)
        {
            int to = L[i].to;
            sum[to]=max(sum[to],sum[e]+val[to]);
            in[to]--;
            if(!in[to]) que.push(to);
            if(F[to]==0) ans = max(ans,sum[to]);
        }
    }
    printf("%d\n",ans);
}
int main()
{
    freopen("in.txt","r",stdin);
    while(~scanf("%d%d",&n,&m))
    {
        init();
        solve();
    }
    return 0;
}