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   Problem Statement  

 Problem Statement for AB

Problem Statement

    

You are given two ints: N and K. Lun the dog is interested in strings that satisfy the following conditions:

  • The string has exactly N characters, each of which is either 'A' or 'B'.
  • The string s has exactly K pairs (i, j) (0 <= i < j <= N-1) such that s[i] = 'A' and s[j] = 'B'.

If there exists a string that satisfies the conditions, find and return any such string. Otherwise, return an empty string.

 

Definition

    
Class:AB
Method:createString
Parameters:int, int
Returns:String
Method signature:String createString(int N, int K)
(be sure your method is public)
    
 

Constraints

-N will be between 2 and 50, inclusive.
-K will be between 0 and N(N-1)/2, inclusive.
 

Examples

0)
    
3
2
Returns: "ABB"
This string has exactly two pairs (i, j) mentioned in the statement: (0, 1) and (0, 2).
1)
    
2
0
Returns: "BA"
Please note that there are valid test cases with K = 0.
2)
    
5
8
Returns: ""
Five characters is too short for this value of K.
3)
    
10
12
Returns: "BAABBABAAB"
Please note that this is an example of a solution; other valid solutions will also be accepted.

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This problem was used for:
       Single Round Match 648 Round 1 - Division I, Level One