1033 To Fill or Not to Fill (25分)

先手动模拟一下算法的流程，可以将走法总结如下（贪心算法）：

1. 如果到达范围内有比当前站更便宜的站，则加油加到刚好能到那个站。
2. 如果到达范围内没有比当前站更便宜的站，那么将油加满，并且选择到达范围内最便宜（但是比当前站贵）的站。

#include<cstdio>
#include<algorithm>
using namespace std;
struct node {
	double price;
	double dis;
}station[500];
bool cmp(node n1, node n2) {
	return n1.dis < n2.dis;
}
const int inf = 0x7fffffff;
int main() {
	int capacity, distance, unitDis, stationNum;
	scanf("%d%d%d%d", &capacity, &distance, &unitDis, &stationNum);
	for (int i = 0;i < stationNum;i++) {
		scanf("%lf%lf", &station[i].price, &station[i].dis);
	}
	station[stationNum].dis = inf;
	sort(station, station + stationNum, cmp);
	if (station[0].dis != 0) {
		printf("The maximum travel distance = 0.00");
		return 0;
	}
	int pos = 0;	//目前位置
	int maxTravel = capacity * unitDis;	//最多可以走的距离
	double cost = 0;	//总花费
	double remain = 0;	//剩下的油量
	while (station[pos].dis < distance) {
		//找到到达范围内下一个更便宜的
		int index = pos + 1,
			nextCheaper = -1,	//下一个比当前站便宜的站
			minPricePos = -1;	//到达范围内最便宜的站
		while (station[index].dis <= station[pos].dis + maxTravel) {
			if (station[index].price < station[pos].price) {
				nextCheaper = index;
				break;
			}
			if (minPricePos == -1 || station[index].price < station[minPricePos].price) {
				minPricePos = index;
			}
			index++;
		}
		if (station[pos].dis + maxTravel >= distance && nextCheaper == -1) {	//当前站可以直接到目的地，且中间没有更便宜的站
			cost += (distance - station[pos].dis - remain * unitDis) / unitDis * station[pos].price;
			break;
		}
		else if (nextCheaper == -1 && minPricePos == -1) {	//到不了下一个站
			printf("The maximum travel distance = %.2lf", station[pos].dis + maxTravel);
			return 0;
		}
		else if (nextCheaper == -1) {	//到达范围内没有更便宜的，加满，去到达范围内最便宜的
			cost += (capacity - remain) * station[pos].price;
			remain = capacity - (station[minPricePos].dis - station[pos].dis) / unitDis;
			pos = minPricePos;
		}
		else {
			cost += (station[nextCheaper].dis - station[pos].dis - remain * unitDis) / unitDis * station[pos].price;
			remain = 0;
			pos = nextCheaper;
		}
	}
	printf("%.2lf", cost);
}