poj 2431 Expedition 貪心

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <queue>using namespace std;const int maxn=1e4+9;int dist,p,n;struct S{    int d,f;    bool operator <(const S & xx) const    {        return d<xx.d;    }}stop[maxn];struct cmp{    bool operator ()(const S &a,const S &b) const    {        return a.f<b.f;    }};int main(){    while(scanf("%d",&n)!=EOF)    {        for(int i=1;i<=n;i++)        scanf("%d %d",&stop[i].d,&stop[i].f);        scanf("%d %d",&dist,&p);        for(int i=1;i<=n;i++)        stop[i].d=dist-stop[i].d;        sort(stop+1,stop+1+n);        int ans=0,t=1;        bool flag=true;        priority_queue <S,vector<S>,cmp> q;        while(p<dist)        {            while(t<=n&&stop[t].d<=p) q.push(stop[t++]);            if(q.empty())            {                flag=false;                break;            }            ans++;            p+=q.top().f;            q.pop();        }        if(flag) cout<<ans<<endl;        else cout<<-1<<endl;    }    return 0;}