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

Write a function to count the total strobogrammatic numbers that exist in the range of low <= num <= high.

Example:

Input: low = "50", high = "100"
Output: 3
Explanation: 69, 88, and 96 are three strobogrammatic numbers.

Note:
Because the range might be a large number, the lowand high numbers are represented as string.

 

这道题是之前那两道 Strobogrammatic Number II 和 Strobogrammatic Number 的拓展,又增加了难度,让找给定范围内的对称数的个数,我们当然不能一个一个的判断是不是对称数,也不能直接每个长度调用第二道中的方法,保存所有的对称数,然后再统计个数,这样 OJ 会提示内存超过允许的范围,所以这里的解法是基于第二道的基础上,不保存所有的结果,而是在递归中直接计数,根据之前的分析,需要初始化 n=0 和 n=1 的情况,然后在其基础上进行递归,递归的长度 len 从 low 到 high 之间遍历,然后看当前单词长度有没有达到 len,如果达到了,首先要去掉开头是0的多位数,然后去掉长度和 low 相同但小于 low 的数,和长度和 high 相同但大于 high 的数,然后结果自增1,然后分别给当前单词左右加上那五对对称数,继续递归调用,参见代码如下:

解法一:

class Solution {
public:
int strobogrammaticInRange(string low, string high) {
int res = ;
for (int i = low.size(); i <= high.size(); ++i) {
find(low, high, "", i, res);
find(low, high, "", i, res);
find(low, high, "", i, res);
find(low, high, "", i, res);
}
return res;
}
void find(string low, string high, string path, int len, int &res) {
if (path.size() >= len) {
if (path.size() != len || (len != && path[] == '')) return;
if ((len == low.size() && path.compare(low) < ) || (len == high.size() && path.compare(high) > )) {
return;
}
++res;
}
find(low, high, "" + path + "", len, res);
find(low, high, "" + path + "", len, res);
find(low, high, "" + path + "", len, res);
find(low, high, "" + path + "", len, res);
find(low, high, "" + path + "", len, res);
}
};

上述代码可以稍微优化一下,得到如下的代码:

解法二:

class Solution {
public:
int strobogrammaticInRange(string low, string high) {
int res = ;
find(low, high, "", res);
find(low, high, "", res);
find(low, high, "", res);
find(low, high, "", res);
return res;
}
void find(string low, string high, string w, int &res) {
if (w.size() >= low.size() && w.size() <= high.size()) {
if (w.size() == high.size() && w.compare(high) > ) {
return;
}
if (!(w.size() > && w[] == '') && !(w.size() == low.size() && w.compare(low) < )) {
++res;
}
}
if (w.size() + > high.size()) return;
find(low, high, "" + w + "", res);
find(low, high, "" + w + "", res);
find(low, high, "" + w + "", res);
find(low, high, "" + w + "", res);
find(low, high, "" + w + "", res);
}
};

Github 同步地址:

https://github.com/grandyang/leetcode/issues/248

类似题目:

Strobogrammatic Number II

Strobogrammatic Number

参考资料:

https://leetcode.com/problems/strobogrammatic-number-iii/

https://leetcode.com/problems/strobogrammatic-number-iii/discuss/67431/My-Java-solution-easy-to-understand

https://leetcode.com/problems/strobogrammatic-number-iii/discuss/67406/Clear-Java-AC-solution-using-Strobogrammatic-Number-II-method

LeetCode All in One 题目讲解汇总(持续更新中...)

[LeetCode] 248. Strobogrammatic Number III 对称数之三的更多相关文章

  1. [LeetCode] 248. Strobogrammatic Number III 对称数III

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

  2. [LeetCode] Strobogrammatic Number III 对称数之三

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

  3. [LeetCode] 247. Strobogrammatic Number II 对称数II

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

  4. [LeetCode] Strobogrammatic Number II 对称数之二

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

  5. [LeetCode] 260. Single Number III 单独数 III

    Given an array of numbers nums, in which exactly two elements appear only once and all the other ele ...

  6. 248. Strobogrammatic Number III

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

  7. [LeetCode] 246. Strobogrammatic Number 对称数

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

  8. [LeetCode] 137. Single Number II 单独数 II

    Given a non-empty array of integers, every element appears three times except for one, which appears ...

  9. LeetCode 246. Strobogrammatic Number

    原题链接在这里:https://leetcode.com/problems/strobogrammatic-number/ 题目: A strobogrammatic number is a numb ...

随机推荐

  1. mysql sql语句摘录

    1.说明:创建数据库 CREATE DATABASE database-name 2.说明:删除数据库 drop database dbname 3.说明:备份sql server --- 创建 备份 ...

  2. vue中toggle切换的3种写法

    前言:查看下面代码,在任意编辑器中直接复制粘贴运行即可 1:非动态组件(全局注册2个组件,借用v-if指令和三元表达式) <!DOCTYPE html> <html> < ...

  3. 打开IDEA的更新选项,如何打开IDEA更新弹窗

    如何让IDEA的更新弹窗重新出现,打开IDEA的更新选项 IDEA  update的时候,会提示一个更新的弹框选择框如下图所示 在最下方有个Do not show this dialog in the ...

  4. 【转】asp.Net Core免费开源分布式异常日志收集框架Exceptionless安装配置以及简单使用图文教程

    最近在学习张善友老师的NanoFabric 框架的时了解到Exceptionless : https://exceptionless.com/ !因此学习了一下这个开源框架!下面对Exceptionl ...

  5. generator的本质是将异步的管理剥离

    generator的本质是将异步的管理剥离

  6. express捕获全局异常的三种方法

    场景 express的路由里抛出异常后,全局中间件没办法捕获,需要在所有的路由函数里写try catch,这坑爹的逻辑让人每次都要多写n行代码 官方错误捕获中件间代码如下 app.use(functi ...

  7. 350道面试题分享,拿下京东offer工资double

    350道面试题分享,拿下京东offer工资double 前言: 面试,其实是一个双向选择的过程,在这个过程里,我们不应该抱着畏惧的心态去对待,这样反而会影响自己的发挥.同时看中的应该不止薪资,还要看你 ...

  8. Vue--运行项目发送http://localhost:8080/sockjs-node/info请求报错,造成浏览器不能热更新

    今早习惯打开vscode 输入 npm run dev 准备修复测试提出的bug 不料一堆通红的报错,让人感到有点绿的慌. 有问题呢,就需要解决问题.经过一番排查后发现是我昨天为了让测试在我本地项目中 ...

  9. 英语chrismatite黄蜡石chrismatite单词

    黄蜡石chrismatite的原岩均为硅质岩,各种原岩受到构造变动.火山活动.热液作用等影响,产生复杂的物理和化学变化,包括重结晶.热变质等,导致矿物成分及结构构造的变化,后受构造变动的影响,岩石露出 ...

  10. Jsp调用淘宝IP地址库获取来访IP详细信息

    Jsp调用淘宝IP地址库获取来访IP详细信息   示例网页点击:www.trembler.cn/ipinfo/ipinfo(服务器有其他用处,页面已失效) String ip = request.ge ...