51nod 1163贪心

    用优先队列来贪心，是一个很好地想法。优先队列在很多时候可以维护最值，同时可以考虑到一些其他情况。

    http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1163

#include<queue>
#include<stack>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define INF 99999999
#define ll __int64
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
const int MAXN = 50010;
struct node
{
    int x;
    int val;
}a[MAXN];
int n;
priority_queue<int, vector<int>, greater<int> >q;
bool cmp(node fa, node fb)
{
    if(fa.x != fb.x)
        return fa.x < fb.x;
    return fa.val > fb.val;
}
int main()
{
    while(cin >>n){
        for(int i = 1; i <= n; i++){
            cin >>a[i].x >> a[i].val;
        }
        sort(a+1, a+n+1, cmp);
        while(!q.empty())q.pop();
        int t = 0;
        for(int i = 1; i <= n; i++){
            if(t < a[i].x){
                t ++;
                q.push(a[i].val);
            }
            else if(t == a[i].x){
                int temp = q.top();
                q.pop();
                if(temp < a[i].val){
                    temp = a[i].val;
                }
                q.push(temp);
            }
        }
        ll ans = 0;
        while(!q.empty()) {
            int temp = q.top();
            q.pop();
            ans += temp;
        }
        cout<<ans<<endl;
    }
}