LeetCode in Kotlin

984. String Without AAA or BBB

Medium

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

class Solution {
    fun strWithout3a3b(a: Int, b: Int): String {
        val first = if (a > b) "a" else "b"
        val second = if (first == "a") "b" else "a"
        var firstLen = a.coerceAtLeast(b)
        var secondLen = a.coerceAtMost(b)
        val ans = StringBuilder()
        // Case 1 : A and B count are unequal.
        while (firstLen > 0 && secondLen > 0 && firstLen != secondLen) {
            ans.append(first)
            ans.append(first)
            firstLen = firstLen - 2
            ans.append(second)
            secondLen--
        }
        // Case 2: A and B count are equal
        while (firstLen > 0 && secondLen > 0) {
            ans.append(first)
            ans.append(second)
            firstLen--
            secondLen--
        }
        // left over, just append
        while (firstLen > 0) {
            ans.append(first)
            firstLen--
        }
        return ans.toString()
    }
}

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