course data time 線段 水題 span uil mini file

Highways

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 2730		Accepted: 1008		Special Judge

Description

In a distant country Lineland there are N cities and they are all located along the highway. The highway is a straight line; it starts from the first city and runs through the second, third city and so on, ending in the N-th city. The i-th city is located at the distance of X i miles from the first one.
The highway is wide and smooth, so it is a pleasure for all people to drive along it. But there is one problem --- all roads in Lineland, including the highway, are one-way. So people are only allowed to drive along the highway from the city with smaller number to the city with greater number and they have to use country roads to get back, and that is not such a great pleasure indeed.
After the new president Mr. Pathwayson was elected in Lineland, he has decided that he would like to make it easier for people to get from one town to another. But he does not dare to change the traditions, and make the highway two-way. Therefore he has decided to build new highways to connect the cities, so that it would be possible to get from any city to any other one by highways. Traditionally, the new highways must be one-way.
Of course, Mr. Pathwayson is a great president, and he wants people to remember him in years. After a thought he has decided that building just one highway would not be enough for that. Therefore he has decided that he must build two new highways. Each highway would connect two different cities. Since people are anxious about their health, and cars running along the highway produce dangerous wastes, each new highway must not pass through any cities, except the cities it connects. Also building two new highways in one city would disturb people too much, so all the cities that would be the ends of the new highways must be different.
You are the assistant of the minister of transportation of Lineland, so you are asked to choose the cities to be connected by the new highways. Since the cost of building a highway is proportional to its length, the total length of the highways must be minimal possible. Write a program to solve this problem. You may assume that the distance between two cities along the new highway is equal to the distance between those cities along the main highway.

Input

The first line of the input contains N (2 <= N <= 50 000).
Next line contains N - 1 integer numbers: X2 , X3 , . . . , XN (1 <= X2 < X3 < . . . < XN <= 10⁹ ).

Output

If it is impossible to build the highways satisfying all requirements, print number 0 on the first line of the output.
In the other case on the first line of the output file print the minimal possible total length of the highways to be built. On the second line print S1 , E1 , S2 and E2 --- the numbers of the cities to connect by the first and the second highway, respectively. Note that highways are one-way and must run from S1 to E1 and from S2 to E2 .

Sample Input

4
3 5 10

Sample Output

12
3 1 4 2

題意是有N個城市在一條快速公路上，這條快速公路是一條直線。可是這條快速公路是單向的，人們去的時候能夠走快速公路。回來的時候又僅僅能走country road了。

所以新上任的市長打算在回去的方向上建立兩條路(事實上一條整個回去的路就足夠了。可是市長任性，就兩條)。滿足路上的城市都能來回都走上快速公路，問修這兩條路的最短距離是多少。

要在回去的方向上修兩條可以在全部城市都能互相來回，說明這兩條路必定反復了一段距離。那既然必定要反復一段距離的話，又要修這兩條路的距離最短，自然要覆蓋那個兩個城市之間最短距離的那個了。

這個題 題意比題都難理解。另外盡管是水題。僅僅須要找這些線段中的最短線段。但我自己還是WA了幾次，原因是要考慮到第一條和最後一條線段是不能被選擇為反復的。原因題目中說了： Each highway would connect two different cities.

代碼：

#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <cstring>
#pragma warning(disable:4996)
using namespace std;

int dis[50002];

int main()
{
	int n,i,min,min_x;
	cin>>n;

	dis[0]=0;
	min=1000000000;
	
	cin>>dis[1];
	
	for(i=2;i<n-1;i++)//得考慮到不是第一條線段和最後一條線段的情況
	{
		cin>>dis[i];
		if(dis[i]-dis[i-1]<min)
		{
			min=dis[i]-dis[i-1];
			min_x=i;
		}
	}
	cin>>dis[n-1];
	
	if(n>=4)
	{
		cout<<min+dis[n-1]<<endl;
		cout<<min_x+1<<" "<<1<<" "<<n<<" "<<min_x<<endl;
	}
	else
	{
		cout<<0<<endl;
	}
	return 0;
}

POJ 2128：Highways