strstr.kt

class Solution {
    fun strStr(source: String, target: String): Int {
        if (target.isEmpty()) {
            return 0
        }
        
        if(source == target) {
            return 0
        }

        var i = 0
        var j = 0
        var result = -1

        while (source.lastIndex >= i) {
            if (j == target.length) {
                return result
            }
            val c: Char = source[i]
            if (c == target[j]) {
                if (j == 0) {
                    result = i
                }
                j++
            } else {
                if (j != 0) {
                    i = result
                }
                j = 0
            }
            i += 1
        }

        
        return if (j == target.length) {
            result
        } else {
            -1
        }
    }
}