poj1852 Ants （模拟）

Ants

Time Limit: 1000MS		Memory Limit: 30000K
Total Submissions: 12810		Accepted: 5606

Description

An army of ants walk on a horizontal pole of length l cm, each with a constant speed of 1 cm/s. When a walking ant reaches an end of the pole, it immediatelly falls off it. When two ants meet they turn back and start walking in opposite directions. We know
the original positions of ants on the pole, unfortunately, we do not know the directions in which the ants are walking. Your task is to compute the earliest and the latest possible times needed for all ants to fall off the pole.
Input

The first line of input contains one integer giving the number of cases that follow. The data for each case start with two integer numbers: the length of the pole (in cm) and n, the number of ants residing on the pole. These two numbers are followed by n integers
giving the position of each ant on the pole as the distance measured from the left end of the pole, in no particular order. All input integers are not bigger than 1000000 and they are separated by whitespace.
Output

For each case of input, output two numbers separated by a single space. The first number is the earliest possible time when all ants fall off the pole (if the directions of their walks are chosen appropriately) and the second number is the latest possible such
time. 

Sample Input

2
10 3
2 6 7
214 7
11 12 7 13 176 23 191

Sample Output

4 8
38 207

Source

Waterloo local 2004.09.19

解析：蚂蚁的速度都是一样的，那么：

          最短时间：蚂蚁向离自己最近的那一端点爬过去

          最长时间：两个蚂蚁相遇，各自反向爬回去，可以看成：两个蚂蚁相遇，交错而过。那么最长时间即为：向着最远端点爬过去的时间。

代码：

#include<cstdio>
#include<algorithm>
using namespace std;

int main()
{
freopen("1.in","r",stdin);

int t,l,n,i,j,ans1,ans2;
scanf("%d",&t);
while(t--)
{
scanf("%d%d",&l,&n);
ans1=ans2=0;
for(i=1;i<=n;i++)
{
scanf("%d",&j);
ans1=max(ans1,min(j,l-j));
ans2=max(ans2,max(j,l-j));
}
printf("%d %d\n",ans1,ans2);
}
return 0;
}