| Train Swapping |
At an old railway station, you may still encounter one of the lastremaining ``train swappers''. A train swapper is an employee ofthe railroad, whose sole job it is to rearrange thecarriages of trains.
Once the carriages are arranged in the optimal order, all the train driver has to do, isdrop 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 stationclose to a railway bridge. Instead of opening up vertically, the bridge rotated around a pillarin 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 twocarriages on it. By rotating the bridge 180 degrees, the carriages switched place, allowing himto 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 toautomate their operation. Part of the program to be developed, is a routine which decidesfor a given train the least number of swaps of two adjacent carriages necessary to order thetrain. 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 oftwo input lines. The first line of a test case contains an integer L, determining the length ofthe train ( 
). The second line of a test case contains a permutation of the numbers1 through L, indicating the current order of the carriages. The carriages should be orderedsuch that carriage 1 comes first, then 2, etc. with carriage L coming last.
Output Specification
For each test case output thesentence: '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. 太水了, 可以用冒泡排序的思路, 然后换一次计数一次~ AC代码:
#include<stdio.h>
#define MAXN 50
int N;
int num[MAXN+5];
int main() {
scanf("%d", &N);
while(N--) {
int l;
int count = 0;
scanf("%d", &l);
for(int i = 0; i < l; i++)
scanf("%d", &num[i]);
for(int i = 0; i < l; i++) {
for(int j = i; j < l; j++) {
if(num[i] > num[j]) {
int t = num[i];
num[i] = num[j];
num[j] = t;
count++;
}
}
}
printf("Optimal train swapping takes %d swaps.
", count);
}
return 0;
}