BZOJ 1572: [Usaco2009 Open] heap of work Job greedy _ go back _

Code:

    for(int i=1;i<=n;++i)
        if(key[i].tim <= (ll)Q.size())  
        {
            if(key[i].val > Q.top()) 
            {
                ans -= Q.top(); 
                ans += key[i].val; 
                Q.pop(); 
                Q.push(key[i].val); 
            }
        }
        else 
        {
            ans += key[i].val; 
            Q.push(key[i].val); 
        }
    }
    printf("%lld\n",ans); 
    return 0; 
}