pat 1033 changed code

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string.h>
#include <cstdio>
using namespace std;
const int inf = 99999999;
struct station {
    double price, dis;
};
bool cmp1(station a, station b) {
    return a.dis < b.dis;
}
int main() {
    double cmax, d, davg;
    int n;
    scanf("%lf%lf%lf%d", &cmax, &d, &davg, &n);
    vector<station> sta(n + 1);
    sta[0] = { 0.0, d };
    for (int i = 1; i <= n; i++)
        scanf("%lf%lf", &sta[i].price, &sta[i].dis);
    sort(sta.begin(), sta.end(), cmp1);
    double nowdis = 0.0, maxdis = 0.0, nowprice = 0.0, totalPrice = 0.0, leftdis = 0.0;
    if (sta[0].dis != 0) {
        printf("The maximum travel distance = 0.00");
        return 0;
    }
    else {
        nowprice = sta[0].price;
    }
    int i = 1;
    while (nowdis < d) {//nowdis mean that distance before the nowdis, price is certain
        maxdis = nowdis + cmax * davg;
        double minPriceDis = 0, minPrice = inf;
        int flag = 0;
        for (; i <= n && sta[i].dis <= maxdis; i++) {
            if (sta[i].price < nowprice) {//if in,add the last dis to totalprice
                totalPrice += (sta[i].dis - nowdis - leftdis) * nowprice / davg;
                leftdis = 0.0;
                nowprice = sta[i].price;
                nowdis = sta[i].dis;
                flag = 1;
                i++;
                break;//jump out the "for" loop
            }


            if (sta[i].price < minPrice) {
                minPrice = sta[i].price;
                minPriceDis = sta[i].dis;
            }
        }

        //to calculate that maximum distance
        if (flag == 0 && minPrice != inf) {
            totalPrice += (nowprice * (cmax - leftdis / davg));
            leftdis = cmax * davg - (minPriceDis - nowdis);//leftdis mean fill the tank with the cheapestPrice ,the distance out the minPricedis
            nowprice = minPrice;
            nowdis = minPriceDis;
        }
        if (flag == 0 && minPrice == inf) {
            nowdis += cmax * davg;
            printf("The maximum travel distance = %.2f", nowdis);
            return 0;
        }

    }
    printf("%.2f", totalPrice);
    return 0;
}