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

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

If needle is empty, return 0.

Input: Two comma-separated strings: haystack and needle.

Output: An integer — the starting index of needle in haystack, or -1 if not found.

Examples

Input: sadbutsad,sad
Output: 0
Explanation: 'sad' first occurs at index 0.

Input: leetcode,leeto
Output: -1
Explanation: 'leeto' is not in 'leetcode'.

Input: hello,ll
Output: 2
Explanation: 'll' starts at index 2.

Constraints

• 1 <= haystack.length, needle.length <= 10^4
• consist of lowercase English letters

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