28. Implement strSTr()

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Implement strStr().

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

解法1：

C++

1

Java

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