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Competition Arena > AB

AB

SRM 648 · 2015-01-29 · by evima

SRM 648 · 2015-01-29 · by evima · Simple Math, String Manipulation
Class Name: AB
Return Type: String
Method Name: createString
Arg Types: (int, int)
Problem Statement

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.

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.

4)
2
1
Returns: "AB"

Submissions are judged against all 86 archived test cases, of which 5 are shown here. Case numbers match the judge’s.

Coding Area

Language: C++17 · define a public class AB with a public method string createString(int N, int K) · 86 test cases · 2 s / 256 MB per case

Submitting as anonymous