Canada Cup 2016 D. Contest Balloons

最近好弱做什么题目都是做一晚上
这是合肥站炼铜后遗症？
这题就是贪心
我已开始还写了1小时………三分…………….

#include<bits/stdc++.h>
using namespace std;
#define sz(X) ((int)X.size())
typedef long long ll;
const int INF = 0x3f3f3f3f;
const int N = 3e5+5;

struct Node{
    int id; ll t, w;
}p[N];
bool cmp1(Node a,Node b) {
    if(a.t != b.t) return a.t < b.t;
    else return a.id > b.id;
}
int main(){
    int n;
    while(~scanf("%d",&n)) {
        priority_queue<ll,vector<ll>,greater<ll>> Q;
        for(int i = 1; i <= n; ++i) {
            scanf("%lld %lld",&p[i].t,&p[i].w); p[i].id = i;
        }
        int ans = INF;
        int tmp = 1;
        sort(p+1, p+n+1,cmp1);

        int fl = 0;
        ll ret = 0; ll pre;
        for(int i = n; i >= 1; --i) {
            if(fl) {
                ret += pre - p[i].t;
                if(pre == p[i].t) {
                    tmp ++; Q.push(p[i].w - p[i].t + 1);
                    continue;
                }
                pre = p[i].t;
                while(!Q.empty()) {
                    ll x = Q.top();
                    if(x > ret) break;
                    Q.pop(); ret -= x; tmp --;
                }
                ans = min(ans, tmp);
                tmp ++; Q.push(p[i].w-p[i].t+1);
            }else {
                if(p[i].id == 1) {
                    fl = 1; ans = min(ans, tmp);
                    pre = p[i].t;
                }else {
                    Q.push(p[i].w-p[i].t+1);
                //  if(n == 7) printf("%lld %d\n",p[i].t,tmp);
                    tmp ++;
                }
            }
        }

        ret += pre;
        while(!Q.empty()) {
            ll x = Q.top();
            if(x > ret) break;
            Q.pop(); ret -= x;  tmp --;
        }
        ans = min(ans, tmp);

        printf("%d\n", ans);
    }
    return 0;
}