題目描寫敘述：

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.

輸入：

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 Di (<=D), the distance between this station and Hangzhou, for i=1,...N. All the numbers in a line are separated by a space.

輸出：

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.

例子輸入：

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 50 1300 12 2 7.10 0 7.00 600

例子輸出：

749.17 The maximum travel distance = 1200.00

來源：

2012年浙江大學計算機及軟件project研究生機試真題

這道題確實挺難的，花了好久的時間，然后自己考慮不全面，最后參考別人的代碼才搞定。

就不敢寫原創了。。。

http://ziliao1.com/Article/Show/73A96AF77079A6C32C4AA82604FCF691

典型的貪心法。

思想就是考慮下一次在何網站加油（從而決定了在本網站須要加多少油）。

考慮這樣幾種情況：

?????1、到達下一網站所需油量?>?油箱最大容量：則下一網站不可達。做法是把油箱加滿，盡可能跑，然后break掉。

?????2、下一網站可達，且油價比本網站廉價：則應盡早“換用”更廉價的油。做法是本站加夠就可以。使得剛好能到達下一站。

?????3、下一網站可達。但油價比本網站貴：此處第一次做錯了，不應該在本站把油箱加滿，而應該繼續尋找滿油的條件下可達的下一個比本站廉價的網站。若找到，則加夠就可以（所以情況2能夠并到這里）；若未找到，則在本站將油箱加滿。

#include <algorithm>#include <iomanip> #include <iostream> using namespace std; struct station { float price; float dist; }; station st[501]; float cmax, d, davg; int n; bool cmp(station a, station b) { return a.dist < b.dist; } // 尋找下一個可達的廉價網站 int nextCheaper(int now) { for(int i = now; i < n; i++) { if(st[i].dist - st[now].dist > cmax * davg) break; if(st[i].price < st[now].price) return i; } return -1; } int main() { while(cin >> cmax) { cin >> d >> davg >> n; for(int i = 0; i < n; i++) cin >> st[i].price >> st[i].dist; st[n].price = -1; st[n].dist = d; n = n + 1; sort(st, st + n, cmp); int nowst = 0; float nowgas = 0; float cost = 0; while(nowst < n - 1) { if(nowst == 0 && st[0].dist != 0) { st[nowst].dist = 0; break; } float needgas = (st[nowst + 1].dist - st[nowst].dist) / davg; if(needgas > cmax) { float addgas = cmax - nowgas; cost += addgas * st[nowst].price; st[nowst].dist += cmax * davg; break; } int nextc = nextCheaper(nowst); if(nextc == -1) { float addgas = cmax - nowgas; nowgas = cmax; cost += addgas * st[nowst].price; nowgas -= needgas; nowst = nowst + 1; }else{ needgas = (st[nextc].dist - st[nowst].dist) / davg; float addgas = needgas - nowgas; if(addgas > 0) { nowgas += addgas; cost += addgas * st[nowst].price; } nowgas -= needgas; nowst = nextc; } } if(nowst == n - 1) cout << fixed << setprecision(2) << cost << endl; else{ float maxdist = st[nowst].dist; cout << "The maximum travel distance = "<< fixed << setprecision(2) << maxdist << endl; } } return 0; }
以下是我模仿大神自己手寫的代碼，差點兒都改動的全然一樣了。。。眼下還是過不了。郁悶

有時間再研究一下啦。。。如今 真的發現不了什么錯誤了

#include <iostream> #include <cstdio> #include <algorithm> using namespace std; struct station {float pri;float dis; }a[999]; int c,d,davg,n; int cmp(station t1,station t2) {return t1.dis<t2.dis; } int next(int now) {for(int i=now+1;i<=n&&a[i].dis-a[now].dis<=c*davg;i++){if(a[i].pri<a[now].pri)return i;}return -1; }int main() {int i;while(cin>>c>>d>>davg>>n){for(i=0;i<n;i++){scanf("%f %f",&a[i].pri,&a[i].dis);}a[n].pri=-1;a[n].dis=d;sort(a,a+n,cmp);// for(i=0;i<n;i++)//printf("%f %f\n",a[i].dis,a[i].pri);int nowst=0;float anspri=0,ansdis=0,nowgas=0;while(nowst<n){if(nowst==0&&a[0].dis!=0){ansdis=0;break;}float needgas=(a[nowst+1].dis-a[nowst].dis)/davg;if(needgas>c){ansdis+=davg*c;break;}int nextst=next(nowst);// printf("%d %d %f\n",nowst,nextst,anspri);if(nextst==-1){anspri+=(c-nowgas)*a[nowst].pri;nowgas=c-needgas;ansdis=a[nowst+1].dis;nowst+=1;}else{float addgas=(a[nextst].dis-a[nowst].dis)/davg-nowgas;if(addgas>0){nowgas=0;anspri+=addgas*a[nowst].pri;}elsenowgas-=needgas;nowst=nextst;ansdis=a[nowst].dis;}}if(nowst==n)printf("%.2f\n",anspri);elseprintf("The maximum travel distance = %.2f\n",ansdis);}return 0; }/**************************************************************Problem: 1437User: HCA1101Language: C++Result: Wrong Answer ****************************************************************/

轉載于:https://www.cnblogs.com/gcczhongduan/p/5266838.html

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