Description
At an old railway station, you may still encounter one of the last remaining ``train swappers''. A train swapper is an employee of the railroad, whose sole job it is to rearrange the carriages of trains.
Once the carriages are arranged in the optimal order, all the train driver has to do, is drop the carriages off, one by one, at the stations for which the load is meant.
The title ``train swapper'' stems from the first person who performed this task, at a station close to a railway bridge. Instead of opening up vertically, the bridge rotated around a pillar in the center of
the river. After rotating the bridge 90 degrees, boats could pass left or right.
The first train swapper had discovered that the bridge could be operated with at most two carriages on it. By rotating the bridge 180 degrees, the carriages switched place, allowing him to rearrange the carriages
(as a side effect, the carriages then faced the opposite direction, but train carriages can move either way, so who cares).
Now that almost all train swappers have died out, the railway company would like to automate their operation. Part of the program to be developed, is a routine which decides for a given train the least number
of swaps of two adjacent carriages necessary to order the train. Your assignment is to create that routine.
Input Specification
The input contains on the first line the number of test cases (N). Each test case consists of two input lines. The first line of a test case contains an integer L, determining the length of
the train ( 
). The second line of a test case contains a permutation of the numbers 1 through L, indicating the current
order of the carriages. The carriages should be ordered such that carriage 1 comes first, then 2, etc. with carriage L coming last.
Output Specification
For each test case output the sentence: 'Optimal train swapping takes S swaps.' where S is an integer.
Example Input
3 3 1 3 2 4 4 3 2 1 2 2 1
Example Output
Optimal train swapping takes 1 swaps. Optimal train swapping takes 6 swaps. Optimal train swapping takes 1 swaps.
解题思路：
还是自己太年轻了，，那道题后，没有认真的想，还在那里一个劲的使劲推公式，把最大的放在最后对于ans的贡献，把次大放在倒数第二个位置对于ans的贡献，，，
QAQ，发现自己还是太年轻了，其实这就是标准的冒泡排序，每次交换后记录下来交换的次数就OK了~
代码：
# include<cstdio>
# include<iostream>
# include<cstring>
using namespace std;
# define MAX 55
int a[MAX];
int main(void)
{
int n;
int t;cin>>t;
while ( t-- )
{
cin>>n;
memset(a,0,sizeof(a));
for ( int i = 0;i < n;i++ )
{
cin>>a[i];
}
int ans = 0;
for ( int i = 1;i < n;i++ )
{
for ( int j = n-1;j >= i;j-- )
{
if ( a[j-1] > a[j] )
{
int t = a[j-1];
a[j-1] = a[j];
a[j] = t;
ans++;
}
}
}
printf("Optimal train swapping takes %d swaps.\n",ans);
}
return 0;
}