Summary Power | Codechef solution

Rajnish Tripathi 05:30

You work as an engineer. You were given an empty board with � consecutive cells; at any moment, each cell can display one character.

You want the board to display a string � with length �>�. Since the board isn't large enough, you want to display the string in �−�+1 steps. In the �-th step (1≤�≤�−�+1), you'll make the board display the characters ��,��+1,…,��+�−1.

The power required to switch the board from step � to step �+1 (for 1≤�≤�−�) is equal to the number of characters displayed on the board that have to change between these steps. You should find the total power required for the whole process of displaying a string, i.e. the sum of powers required for switching between all consecutive pairs of steps.

Input

  • The first line of the input contains a single integer � denoting the number of test cases. The description of � test cases follows.
  • The first line of each test case contains two space-separated integers � and �.
  • The second line contains a single string � with length �.

Output

For each test case, print a single line containing one integer — the total power required for text switching.

Constraints

  • 1≤�≤1,000
  • 2≤�≤105
  • 1≤�<�
  • each character of � is a lowercase English letter
  • the sum of � for all test cases does not exceed 106

Subtasks

Subtask #1 (20 points):

  • 1≤�≤100
  • 2≤�≤50

Subtask #2 (80 points): original constraints

Sample 1:

Input
Output
3
6 3
aabbcc
5 2
abccc
4 3
aabb
4
3
1

Explanation:

Example case 1:

  • In step 1, the board is displaying "aab".
  • In step 2, the board is displaying "abb".
  • In step 3, the board is displaying "bbc".
  • In step 4, the board is displaying "bcc".

The power required for switching from the 1-st to the 2-nd step is 1, because cell 1 changes from 'a' to 'a' (requiring power 0), cell 2 changes from 'a' to 'b' (requiring power 1) and cell 3 changes from 'b' to 'b' (requiring power 0); 0+1+0=1.

The power required for switching between the 2-nd and 3-rd step is 2 and the power required for switching between the 3-rd and 4-th step is 1.

Therefore, the answer is 1+2+1=4.

 Code(C++):-


Code(JAVA):-

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