[Solved] 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.

Question

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.

Python Solution

class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        if needle=="":
            return 0
        else:
            for i in range(len(haystack)):
                if haystack[i]==needle[0]:
                    if haystack[i:i+len(needle)]==needle:
                        return i
            
            return -1