左旋转字符串

题目

字符串左移k位后的结果

解题

旋转三次

public class Solution {
    public String LeftRotateString(String str,int n) {
        if(str == null || str.length() <=1)
            return str;
        int len= str.length();
        n = n%len;
        char[] A = str.toCharArray();
        reverse(A,0,len-1);
        reverse(A,0,len-n-1);
        reverse(A,len-n,len-1);
        return String.valueOf(A);
    }
    // 旋转
    public void reverse(char[] A,int left, int right){
        int i = left;
        int j = right;
        while(i<j){
            swap(A,i,j);
            i++;
            j--;
        }
    }
    // 交换
    public void swap(char[] A,int i,int j){
        char ch = A[i];
        A[i] = A[j];
        A[j] = ch;
    }
}