8. Rotate String

8. Rotate String

Description

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

Example

Given "abcdefg".

offset=0 => "abcdefg"
offset=1 => "gabcdef"
offset=2 => "fgabcde"
offset=3 => "efgabcd"

Challenge

Rotate in-place with O(1) extra memory.

三步旋转法：

1.将末尾offset个字符旋转
2.将 0- (length-ofset)字符 旋转
3.将全部的字符旋转

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(offset == 0 )
            return;
        if(str.length == 0)
            return;
        for(int i = 0; i < offset%str.length; i++)
        {
            char temp = str[str.length-1];
            int j = str.length-2;
            while(j >= 0)
            {
                str[j+1] = str[j];
                j--;

            }
            str[0] = temp;
        }
    }
}

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.length==0){
            return;
        }
        if(offset==0){
            return;
        }else if(offset%str.length==0){
            return;
        }else{
            offset=offset%str.length;
            int[] temp=new int[offset];
            for(int i=str.length-offset;i<str.length;i++){
                temp[i-str.length+offset]=str[i];
            }
            /*for(int j=0;j<temp.length;j++){
                System.out.println((char)temp[j]);
            }*/
            for(int i=str.length-offset-1;i>=0;i--){
    		    str[i+offset]=str[i];
		    }
		    for(int i=0;i<offset;i++){
    			str[i]=(char)temp[i];
		    }
        }
    }
}

给定一个字符串和一个偏移量，根据偏移量旋转字符串(从左向右旋转)