Basic exercises-the perfect price and the cost of exercises

Basic exercises-the perfect price and the cost of exercises

Problem description
A return string is a special string that reads from left to right and from right to left. Xiao Long believes that the reply string is perfect. Now, I will give you a string. It is not necessarily a return string. Please calculate the minimum number of exchanges to make the string a perfect return string.
Two adjacent characters are exchanged.
For example, mamad
First switching ad: mamda
Second exchange md: madma
The third ma exchange: madam (reply! Perfect !)
Input Format
The first line is an integer N, indicating the length of the subsequent string (N <= 8000)
The second line is a string with a length of N. It only contains lowercase letters.
Output Format
If possible, the minimum number of exchanges is output.
Otherwise, output Impossible.
Sample Input
5
Mamad
Sample output
3

 

#include <cstdio>  #include <cstdlib>    int main()  {  #ifdef LOCAL      freopen("input2.txt", "r", stdin);  #endif      int n, flag = 0, ans = 0;      char *str;      scanf("%d", &n);      str = (char*)malloc(n * sizeof(char));      scanf("%s", str);      int j = n - 1, p = 0;      for(int i = 0; i < j; i++)      {          for(int k = j; k >= 0; k--)          {              if(k == i)              {                  flag++;                  if(n % 2 == 0 || flag > 1)                  {                      printf("Impossible\n");                      return 0;                  }                  p = n/2 - i;                  break;              }              else if(str[k] == str[i])              {                  ans += j - k;              //  printf("ans = %d\n", ans);                  for(int f = k; f < j; f++)                  {                      str[f] = str[f + 1];                  }                  str[j] = str[i];                  j--;                  break;              }           }      }      printf("%d\n", ans + p);      return 0;  }