Решение

class Solution {
    fun isPrefixOfWord(sentence: String, searchWord: String): Int {
        val n = sentence.length
        val m = searchWord.length
        var i = 0
        var idx = 1
        while (i < n) {
            while (i < n && sentence[i] == ' ') i++
            if (i >= n) break
            var j = 0
            var k = i
            while (j < m && k < n && sentence[k] == searchWord[j]) { j++; k++ }
            if (j == m) return idx
            while (k < n && sentence[k] != ' ') k++
            idx++
            i = k
        }
        return -1
    }
}