LeetCode 28 Implement strStr()

题目：

Implement strStr().

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

Example 1:

Input: haystack = "hello", needle = "ll"
Output: 2

Example 2:

Input: haystack = "aaaaa", needle = "bba"
Output: -1

Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().

解法：

字符串匹配，算法有很多，BF，KMP等等，因为这是个简单题，所以这里用最简单的暴力解法BF（其实其他的我还不会写）

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