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pat _1033 To Fill or Not to Fill


原题说明：


With highways available, driving a car from Hangzhou to any other city is easy. But since the tank capacity of a car is limited, we have to find gas stations on the way from time to time. Different gas station may give different price. You are asked to carefully design the cheapest route to go.

I

nput Specification:


Each input file contains one test case. For each case, the first line contains 4 positive numbers: Cmax(≤ 100), the maximum capacity of the tank; D (≤30000), the distance between Hangzhou and the destination city; Davg(≤20), the average distance per unit gas that the car can run; and N (≤ 500), the total number of gas stations. Then N lines follow, each contains a pair of non-negative numbers: Pi, the unit gas price, and D​i(≤D), the distance between this station and Hangzhou, for i=1,⋯,N. All the numbers in a line are separated by a space.


Output Specification:


For each test case, print the cheapest price in a line, accurate up to 2 decimal places. It is assumed that the tank is empty at the beginning. If it is impossible to reach the destination, print The maximum travel distance = X where X is the maximum possible distance the car can run, accurate up to 2 decimal places.

Sample Input 1:

50 1300 12 8

6.00 1250

7.00 600

7.00 150

7.10 0

7.20 200

7.50 400

7.30 1000

6.85 300

Sample Output 1:

749.17

Sample Input 2:

50 1300 12 2

7.10 0

7.00 600

Sample Output 2:

The maximum travel distance = 1200.00


我的代码：

#include

#include

using namespace std;

struct station{


double dis,price;

}p[500];

bool cmp(station a,station b)

{


return a.dis<b.dis;

}

int main()

{


double cost=0,tankcapacity,des,disperunit,nowtank=0;

int now=0,n;

scanf(“%lf%lf%lf%d”,&tankcapacity,&des,&disperunit,&n);

for(int i=0;i<n;i++)

{


scanf(“%lf%lf”,&p[i].price,&p[i].dis);

}

p[n].dis=des,p[n].price=0;

sort(p,p+n,cmp);

if(p[0].dis!=0)//这里是真的坑，测试点2老是过不了，原来它是车一开始没有油，所以最远距离是0，现实中哪有上来就没油的

{


printf(“The maximum travel distance = 0.00”);

return 0;

}

while(1)

{ int next=now+1;

if((p[next].dis-p[now].dis)>tankcapacity

disperunit)

{ double farest=p[now].dis+tankcapacity

disperunit;

printf(“The maximum travel distance = %.2f”,farest);

return 0;

}

int flag=0,min=next;

while(next<n&&(p[next].dis-p[now].dis<=tankcapacity*disperunit))

{


if(p[next].price<=p[now].price)

{


cost+=((p[next].dis-p[now].dis)/disperunit-nowtank)*p[now].price;

now=next;

flag=1;

break;

}

else next++;

}

    if(flag==0)
    {   next=now+1;
        cost+=(tankcapacity-nowtank)*p[now].price;
        nowtank=tankcapacity;
        while(next<n&&(p[next].dis-p[now].dis<=tankcapacity*disperunit))
        {
            if(p[min].price>=p[next].price)
            {
                min=next;
            }
             next++;
        }
        nowtank-=(p[min].dis-p[now].dis)/disperunit;
        now=min;
    }
    next=now+1;
    while(p[next].price>p[now].price&&next<n)
    {   
        next++;
    }
    if(next==n&&p[next].dis-p[now].dis<=tankcapacity*disperunit)
    {
        cost+=(des-p[now].dis)/disperunit*p[now].price;
        printf("%.2f\n",cost);
        return 0;
    }       
}
return 0;

}