剑指Offer——左旋转字符串

 public String LeftRotateString(String str,int n) {
        String result = "";
        if (str == null || str.length() == 0) {
            return result;
        }
        if (n <= 0 || n == str.length()) {
            return str;
        }
        char[] chars = str.toCharArray();
        //外层循环控制的左移的次数
        for (int i = 0; i < n % str.length(); i++) {
            char temp = chars[0];
            //每次左移都是从第二个字符开始的
            for (int k = 1; k < chars.length; k++) {
                chars[k - 1] = chars[k];
            }
            chars[chars.length - 1] = temp;
        }
        result = String.valueOf(chars);
        return result;
    }