Merge strings alternately

class Solution {
    fun mergeAlternately(word1: String, word2: String): String {
        val merged = StringBuilder()
        var i = 0
        var j = 0

        while (i < word1.length && j < word2.length) {
            merged.append(word1[i++])
            merged.append(word2[j++])
        }

        merged.append(word1.substring(i))
        merged.append(word2.substring(j))

        return merged.toString()
    }
}