[LeetCode] 28. Implement strStr()

Implement strStr().
Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Thought process:
Iterate through haystack. When I find the first character of needle, iterate through needle. Check if all the rest of the characters match.

Solution:

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class Solution {
    public int strStr(String haystack, String needle) {
        for (int i = 0; i < haystack.length() - needle.length() + 1; i++) {
            if (haystack.substring(i, i + needle.length()).equals(needle)) {
                return i;
            }
        }
        return -1;
    }
}

Time complexity:
Say the length of haystack is h and needle is n. The overall time complexity is O((h - n)n).
Location: Philadelphia, PA, USA

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