題目

給定一個(gè)字符串和一個(gè)偏移量，根據(jù)偏移量旋轉(zhuǎn)字符串(從左向右旋轉(zhuǎn))

樣例
對(duì)于字符串 "abcdefg".
offset=0 => "abcdefg"
offset=1 => "gabcdef"
offset=2 => "fgabcde"
offset=3 => "efgabcd"

分析

旋轉(zhuǎn)字符串在原地旋轉(zhuǎn)，利用了一個(gè)技巧，旋轉(zhuǎn)三次可以達(dá)到效果，具體看代碼分析即可。這種旋轉(zhuǎn)的技巧需要熟練掌握

代碼

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 = offset % str.length;
        reverse(str, 0, str.length - offset - 1);
        reverse(str, str.length - offset, str.length - 1);
        reverse(str, 0, str.length - 1);
    }
    
    private void reverse(char[] str, int start, int end) {
        for (int i = start, j = end; i < j; i++, j--) {
            char temp = str[i];
            str[i] = str[j];
            str[j] = temp;
        }
    }
}