【LeetCode】 Implement strStr()

序号：28

难度：easy

题目简述：

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().

字符串匹配问题，目前使用Brute-Force的方法解决，听说KMP是解决这类问题的主要方法，之后再学  。

class Solution {
    public int strStr(String haystack, String needle) {
        String h = haystack;
        String n = needle;
        if("".equals(n)) return 0;
       for(int i = 0;i <= h.length() - n.length();i++){
           for(int j = 0; h.charAt(i+j) == n.charAt(j) && j < n.length();j++)
               if(j == n.length() - 1) return i;
       }
        return -1;
    }
}