Implement strStr()

Implement strStr()

Implement strStr().

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

Update (2014-11-02):
The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a char * or String, please click the reload button to reset your code definition.

Java代码：

public class Solution {
    public int strStr(String haystack, String needle) {
        if(haystack.length()<needle.length())
			return -1;
		if(needle.length()==0)return 0;
		int len = haystack.length();
		for(int i=0;i<haystack.length();i++){
			for(int j=0,k=0;j<needle.length();j++){
				if((i+k)==haystack.length())
					return -1;
				if(haystack.charAt(i+k) != needle.charAt(j))
					break;
				else
				{
					k++;
					if(k==needle.length())
						return i;
				}
			}
		}
		return -1;
    }
}