LeetCode in Kotlin

3456. Find Special Substring of Length K

Easy

You are given a string s and an integer k.

Determine if there exists a substring of length exactly k in s that satisfies the following conditions:

1. The substring consists of only one distinct character (e.g., "aaa" or "bbb").
2. If there is a character immediately before the substring, it must be different from the character in the substring.
3. If there is a character immediately after the substring, it must also be different from the character in the substring.

Return true if such a substring exists. Otherwise, return false.

Example 1:

Input: s = “aaabaaa”, k = 3

Output: true

Explanation:

The substring s[4..6] == "aaa" satisfies the conditions.

• It has a length of 3.
• All characters are the same.
• The character before "aaa" is 'b', which is different from 'a'.
• There is no character after "aaa".

Example 2:

Input: s = “abc”, k = 2

Output: false

Explanation:

There is no substring of length 2 that consists of one distinct character and satisfies the conditions.

Constraints:

• 1 <= k <= s.length <= 100
• s consists of lowercase English letters only.

Solution

class Solution {
    fun hasSpecialSubstring(s: String, k: Int): Boolean {
        var start = 0
        var end = k
        while (end <= s.length) {
            var flag = false
            var i = start
            while (i < end - 1) {
                if (s[i] != s[i + 1]) {
                    start++
                    end++
                    flag = true
                    break
                }
                i++
            }
            if (flag) {
                continue
            }
            if (start - 1 >= 0 && s[start] == s[start - 1] ||
                end < s.length && s[end] == s[end - 1]
            ) {
                start++
                end++
            } else {
                return true
            }
        }
        return false
    }
}

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