首先我们可以发现如果错过了一个加油站,而继续往前走的时候没有油了,可以再假装之前经过加油站的时候加过油
于是我们维护一个大根堆,表示错过的加油站是哪些,每当没有油的时候从堆顶取出最大值加上去即可
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 /************************************************************** 2 Problem: 1747 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:20 ms 7 Memory:916 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <algorithm> 12 #include <queue> 13 14 using namespace std; 15 const int N = 1e4 + 5; 16 17 inline int read(); 18 19 struct data { 20 int w, add; 21 22 inline void get() { 23 w = read(), add = read(); 24 } 25 26 inline bool operator < (const data &d) const { 27 return w > d.w; 28 } 29 } a[N]; 30 31 int n, tot, ans; 32 priority_queue <int> h; 33 34 int main() { 35 int i; 36 n = read(); 37 for (i = 1; i <= n; ++i) a[i].get(); 38 a[0].w = read(), tot = read(); 39 sort(a + 1, a + n + 1); 40 a[n + 1].w = 0; 41 for (i = 1; i <= n + 1; ++i) { 42 tot -= (a[i - 1].w - a[i].w); 43 while (tot < 0 && !h.empty()) { 44 ++ans; 45 tot += h.top(), h.pop(); 46 } 47 if (tot < 0) { 48 puts("-1"); 49 return 0; 50 } 51 h.push(a[i].add); 52 } 53 printf("%d\n", ans); 54 return 0; 55 } 56 57 inline int read() { 58 static int x; 59 static char ch; 60 x = 0, ch = getchar(); 61 while (ch < '0' || '9' < ch) 62 ch = getchar(); 63 while ('0' <= ch && ch <= '9') { 64 x = x * 10 + ch - '0'; 65 ch = getchar(); 66 } 67 return x; 68 }
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