• Source 
    1. #include <iostream>
    2. using namespace std;
    3.  
    4. int main ()
    5. {
    6. 	int n, k;
    7. 	cin>>n>>k;
    8. 	char arr[100005];
    9. 	for (int i=1; i<=n; i++)
    10. 	{
    11. 		cin>>arr[i];
    12. 	}
    13.  
    14. 	int diff_pair=0;
    15. 	int same_pair=0;
    16. 	for (int i=1, j=n; i<=n, j>=1; i++, j--)
    17. 	{
    18. 		if (i>=j) break;
    19. 		if (arr[i]!=arr[j]) diff_pair++;
    20. 		else if (arr[i]==arr[j]) same_pair++;
    21. 	}
    22. 	if (k>n) cout<<"No";
    23. 	else if (k==n) cout<<"Yes";
    24. 	else
    25. 	{
    26. 		int kt=0;
    27. 		for (int i=0; i<=diff_pair; i++)
    28. 		{
    29. 			int change=1*i+(diff_pair-i)*2;
    30. 			if (change==k)
    31. 			{
    32. 				kt=1;
    33. 				break;
    34. 			}
    35. 			else
    36. 			{
    37. 				if (change<k)
    38. 				{
    39. 					int Excess = k-change;
    40. 					if (n%2!=0)
    41. 					{
    42. 						int change_max = same_pair*2;
    43. 						if (Excess<=change_max+1)
    44. 						{
    45. 							kt=1;
    46. 							break;
    47. 						}
    48. 					}
    49. 					else
    50. 					{
    51. 						int change_max = same_pair*2;
    52. 						if (Excess<=change_max && Excess%2==0)
    53. 						{
    54. 							kt=1;
    55. 							break;
    56. 						}
    57. 					}
    58. 				}
    59. 			}
    60. 		}
    61. 		if (kt==1) cout<<"Yes";
    62. 		else cout<<"No";
    63. 	}
    64. 	return 0;
    65. }