Lintcode: Rotate String

Given a string and an offset, rotate string by offset. (rotate from left to right)

Example
Given "abcdefg"

for offset=0, return "abcdefg"

for offset=1, return "gabcdef"

for offset=2, return "fgabcde"

for offset=3, return "efgabcd"

需要注意的是：if (A.length == 0) return new char[0]; 空数组

public class Solution {
    /*
     * param A: A string
     * param offset: Rotate string with offset.
     * return: Rotated string.
     */
    public char[] rotateString(char[] A, int offset) {
        // wirte your code here
        if (A==null || A.length == 0) return new char[0];
        String str = new String(A);
        offset %= str.length();
        if (offset == 0) return str.toCharArray();
        String first = str.substring(0, str.length()-offset);
        String second = str.substring(str.length()-offset);
        String res = second + first;
        return res.toCharArray();
    }
};

 法二（推荐）：

public class Solution {
    /**
     * @param str: an array of char
     * @param offset: an integer
     * @return: nothing
     */
    public void rotateString(char[] str, int offset) {
        // write your code here
        if (str==null || str.length==0) return;
        offset %= str.length;
        if (offset == 0) return;
        reverse(str, 0, str.length-1);
        reverse(str, 0, offset-1);
        reverse(str, offset, str.length-1);
    }
    
    public void reverse(char[] str, int l, int r) {
        
        while (l < r) {
            char temp = str[l];
            str[l] = str[r];
            str[r] = temp;
            l++;
            r--;
        }
    }
}