POJ 2431 Expedition

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 struct node{
18     int x,y;
19     node(int a = 0,int b = 0){
20         x = a;
21         y = b;
22     }
23 };
24 node p[10010];
25 bool cmp(const node &a,const node &b){
26     return a.x < b.x;
27 }
28 priority_queue<int,vector<int>,less<int> >q;
29 int main() {
30     int n,L,pnow,pos = 0,ans = 0;
31     scanf("%d",&n);
32     for(int i = 0; i < n; i++)
33         scanf("%d %d",&p[i].x,&p[i].y);
34 
35     scanf("%d %d",&L,&pnow);
36     for(int i = 0; i < n; i++)
37         p[i].x = L-p[i].x;
38     p[n].x = L;
39     p[n++].y = 0;
40     sort(p,p+n,cmp);
41     for(int i = 0; i < n; i++){
42         int d = p[i].x - pos;
43         while( pnow - d < 0){
44             if(q.empty()) {
45                 puts("-1");
46                 return 0;
47             }
48             pnow += q.top();
49             q.pop();
50             ans++;
51         }
52         pnow -= d;
53         pos = p[i].x;
54         q.push(p[i].y);
55     }
56     printf("%d\n",ans);
57     return 0;
58 }