String FAQ

1. Rotate the string

　　1.str1="1234",str2="2341"

　　2. Determine whether str2 is the rotation string of str1:

　　　　1.str=str1+str1 ，即"12341234"

　　　　2. Use the kmp algorithm (O(m+n)) to determine whether str contains str2

　　3. Any substring of length N in str is a rotated string of str1.

2. String reverse order

　　str1="god i like you." 变为str2="you like i god"

　　step:

　　　　1. Reverse the string to ".uoy ekil i dog"

　　　　2. Reverse word by word, "you. like i god"

　　　　3. Reverse method:

　　　　　Reverse by parity of string length.