LeetCode in Kotlin

28. Find the Index of the First Occurrence in a String

Medium

Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Example 1:

Input: haystack = “sadbutsad”, needle = “sad”

Output: 0

Explanation: “sad” occurs at index 0 and 6. The first occurrence is at index 0, so we return 0.

Example 2:

Input: haystack = “leetcode”, needle = “leeto”

Output: -1

Explanation: “leeto” did not occur in “leetcode”, so we return -1.

Constraints:

• 1 <= haystack.length, needle.length <= 104
• haystack and needle consist of only lowercase English characters.

Solution

class Solution {
    fun strStr(haystack: String, needle: String): Int {
        if (needle.isEmpty()) {
            return 0
        }
        val m = haystack.length
        val n = needle.length
        for (start in 0 until m - n + 1) {
            if (haystack.substring(start, start + n) == needle) {
                return start
            }
        }
        return -1
    }
}

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