POJ 2431Expedition

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <queue>
 4 
 5 using namespace std;
 6 const int MAXN = 10000 + 10;
 7 int L, P, N;
 8 struct node{
 9     int a, b;
10 }p[MAXN];
11 
12 bool cmp(const struct node p1, const struct node p2)
13 {
14     return p1.a < p2.a;
15 }
16 
17 void solve()
18 {
19     p[N].a = L;
20     p[N].b = 0;
21     N++;
22 
23     priority_queue<int> que;
24     int pos = 0, tank = P, ans = 0;
25     for(int i = 0; i != N; ++i)
26     {
27         int d = p[i].a - pos;
28         while(tank - d < 0)
29         {
30             if(que.empty())
31             {
32                 puts("-1");
33                 return;
34             }
35             tank += que.top();
36             que.pop();
37             ans++;
38         }
39         tank -= d;
40         pos = p[i].a;
41         que.push(p[i].b);
42     }
43     printf("%d\n", ans);
44 }
45 
46 int main()
47 {
48     //freopen("in.txt", "r", stdin);
49     while(~scanf("%d" ,&N))
50     {
51        for(int i = 0; i != N; ++i)
52        {
53            scanf("%d %d", &(p[i].a), &(p[i].b));
54            //printf("%d %d\n", p[i].a, p[i].b);
55        }
56 
57        scanf("%d %d", &L, &P);
58         for(int i = 0; i != N; ++i)
59             p[i].a = L - p[i].a;
60         sort(p, p+N, cmp);
61 
62         solve();
63     }
64     return 0;
65 }