Problem:

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

Analysis:

This kind of problem is very very easy!!! Keep clam and carry on!
Basic idea:
1. identify which digits are valid for construct a Strobogrammatic Number.
Instant idea: 0, 1, 8.
Hint from the question: 6, 9
private boolean isStroboDigit(Character c) {
if (c == '0' || c == '1' || c == '6' || c == '8' || c == '9')
return true;
return false;
} 2. To look a num upside own is equal to reverse it. (with '6' change into '9', '9' change into '6')
char c = num.charAt(i);
if (isStroboDigit(c)) {
if (c == '6')
buffer.append('9');
else if(c == '9')
buffer.append('6');
else
buffer.append(c);
} else {
return false;
} My common mistakes in implementation:
1. write : (forget to change i++ into i--, when realizing we should scan from the last charcter!)
for (int i = len - 1; i >= 0; i--)
into
for (int i = len - 1; i >= 0; i++) 2. return buffer.toString.equals(num);
Forget () after toString method.

Solution:

public class Solution {
public boolean isStrobogrammatic(String num) {
if (num == null)
throw new IllegalArgumentException("num is null");
int len = num.length();
if (len == 0)
return true;
StringBuffer buffer = new StringBuffer();
for (int i = len - 1; i >= 0; i--) {
char c = num.charAt(i);
if (isStroboDigit(c)) {
if (c == '6')
buffer.append('9');
else if(c == '9')
buffer.append('6');
else
buffer.append(c);
} else {
return false;
}
}
return buffer.toString().equals(num);
} private boolean isStroboDigit(Character c) {
if (c == '0' || c == '1' || c == '6' || c == '8' || c == '9')
return true;
return false;
}
}

[LeetCode#246] Missing Ranges Strobogrammatic Number的更多相关文章

  1. [LeetCode#159] Missing Ranges Strobogrammatic Number

    Problem: Given a string, find the length of the longest substring T that contains at most 2 distinct ...

  2. LeetCode 163. Missing Ranges (缺失的区间)$

    Given a sorted integer array where the range of elements are in the inclusive range [lower, upper], ...

  3. [LeetCode#163] Missing Ranges

    Problem: Given a sorted integer array where the range of elements are [lower, upper] inclusive, retu ...

  4. [leetcode]163. Missing Ranges缺失范围

    Given a sorted integer array nums, where the range of elements are in the inclusive range [lower, up ...

  5. [LeetCode] 163. Missing Ranges 缺失区间

    Given a sorted integer array nums, where the range of elements are in the inclusive range [lower, up ...

  6. ✡ leetcode 163. Missing Ranges 找出缺失范围 --------- java

    Given a sorted integer array where the range of elements are in the inclusive range [lower, upper], ...

  7. 【LeetCode】Missing Ranges

    Missing Ranges Given a sorted integer array where the range of elements are [lower, upper] inclusive ...

  8. [LeetCode] 228. Summary Ranges 总结区间

    Given a sorted integer array without duplicates, return the summary of its ranges. Example 1: Input: ...

  9. LeetCode 246. Strobogrammatic Number (可颠倒数字) $

    A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside ...

随机推荐

  1. CentOS7安装Puppet+GitLab+Bind

    添加Puppet官方源 rpm -Uvh https://yum.puppetlabs.com/puppetlabs-release-el-7.noarch.rpm 安装Puppet yum -y i ...

  2. 什么是JavaScript?

  3. 学习完毕-css

    最近零零散散学习了css 最后附带链接,里面有css的全部demo.有空的可以练习练习,下一步 --->js -----http://www.w3cschool.cc/css/css-examp ...

  4. 使用DataList 分页方法

    什么是DataList我想应该不需要解释了,接下来分享本人在项目里使用到的通过DataList进行分页展示方法. 首先在ASPX页面添加一个DataList(后面都简称DL)控件,示例代码如下: &l ...

  5. js文件缓存之版本管理

    以前也做过不少项目,但从来就没有把关注的目光投向过js文件缓存.最近终于在毫无意识的情况下跳进了这个大坑. 近几个月来的工作是一个交易系统持续改进项目,迭代发布周期大约为2~3周.最近一次迭代是V16 ...

  6. Objective c 自动释放池

    学IOS 的大家都知道,IOS 一共有三种内存管理方式:MRC .ARC.自动释放池.我按照我个人的理解简述一下自动释放池,希望能给大家一点帮助,如有错误请大家及时批评指正. 自动释放池有几个特点:1 ...

  7. AngularJS cookie的使用

    Javascript使用document.cookie接口来处理简单的文本cookie,但现在大多数现代浏览器都可以使用html5 API了(sessionstorage和localstorage), ...

  8. 图解数据结构树之AVL树

    AVL树(平衡二叉树): AVL树本质上是一颗二叉查找树,但是它又具有以下特点:它是一棵空树或它的左右两个子树的高度差的绝对值不超过1,并且左右两个子树都是一棵平衡二叉树.在AVL树中任何节点的两个子 ...

  9. C++类型转换总结 转

    一.前言: C风格的强制类型转换(Type Cast)很简单,不管什么类型的转换统统是: TYPE b = (TYPE)a. C++风格的类型转换提供了4种类型转换操作符来应对不同场合的应用. con ...

  10. select源码分析(linux2.6.11)

    本文以tcp poll为例子来分析select的源码,下面是函数调用顺序.select--->sys_select->do_select--->sock_poll--->tcp ...