The First Occurrence of Needle In Haystack

The problem is:

Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

A naive method: (1) find the the first letter of needle in haystack, (2)comparing other consecutive characters of needle and haystack, (3) if all letters in needle can be found in haystack consecutively, then return the position in haystack.

- See more at: http://bo-yang.github.io/2014/07/01/strstr/#sthash.dvdv0jfs.dpuf

 http://bo-yang.github.io/2014/07/01/strstr