Implement strStr()

Problem: Implement strStr()

Just scan the string to solve the problem.

Code in Python:

class Solution(object):
    def strStr(self, haystack, needle):
        """
        :type haystack: str
        :type needle: str
        :rtype: int
        """
        m, n = len(haystack), len(needle)

        for i in xrange(m-n+1):
            if haystack[i:i+n] == needle: return i
        return -1

Code in Java:

public class Solution {
    public int strStr(String haystack, String needle) {
        int m = haystack.length(), n = needle.length();

        for (int i = 0; i <= m-n; i++) {
            if (haystack.substring(i, i+n).equals(needle))
                return i;
        }
        return -1;
    }
}