984. String Without AAA or BBB

Problem Link

Description

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Given two integers a and b, return any string s such that:

• s has length a + b and contains exactly a 'a' letters, and exactly b 'b' letters,
• The substring 'aaa' does not occur in s, and
• The substring 'bbb' does not occur in s.

 

Example 1:

Input: a = 1, b = 2
Output: "abb"
Explanation: "abb", "bab" and "bba" are all correct answers.

Example 2:

Input: a = 4, b = 1
Output: "aabaa"

 

Constraints:

• 0 <= a, b <= 100
• It is guaranteed such an s exists for the given a and b.

Solution

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Python3

class Solution:
    def strWithout3a3b(self, a: int, b: int) -> str:
        res = ""
        
        
        while a > 0 and b > 0:
            if a > b:
                res += "a" * min(a, 2)
                res += "b"
                a -= min(a, 2)
                b -= 1
            elif a == b:
                if not res or res[-1] == "a":
                    res += "b"
                    b -= 1
                else:
                    res += "a"
                    a -= 1
            else:
                res += "b" * min(b, 2)
                res += "a"
                b -= min(b, 2)
                a -= 1
        
        if a > 0:
            res += "a" * a
        
        if b > 0:
            res += "b" * b
        
        return res