[LeetCode] 247. Strobogrammatic Number II

GHOST_349178 发布于2019-08-16 13:50 / 1482人阅读

Problem

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

Find all strobogrammatic numbers that are of length = n.

Example:

Input: n = 2
Output: ["11","69","88","96"]

Solution

</>复制代码 
class Solution {
    public List findStrobogrammatic(int n) {
        List res = new ArrayList<>();
        if (n == 0) return res;
        if (n == 1) return Arrays.asList("0", "1", "8");
        Map map = new HashMap();
        map.put("0", "0");
        map.put("1", "1");
        map.put("6", "9");
        map.put("8", "8");
        map.put("9", "6");
        dfs(map, new char[n], 0, n, res);
        return res;
    }
    private void dfs(Map map, char[] buffer, int index, int n, List res) {
        // when index just passed the mid point, (n+1)/2 works for both odd and even
        if (index == (n+1)/2) {
            res.add(String.valueOf(buffer));
            return;
        }
        for (char ch: map.keySet()) {
            if (index == 0 && n > 1 && ch == "0") continue;
            if (index == n/2 && (ch == "6" || ch == "9")) continue;
            buffer[index] = ch;
            buffer[n-1-index] = map.get(ch);
            dfs(map, buffer, index+1, n, res);
        }
    }
}

云服务器 GPU云服务器 Strobogrammatic tokyo247 LeetCode LeetCode_String

文章版权归作者所有，未经允许请勿转载,若此文章存在违规行为，您可以联系管理员删除。

转载请注明本文地址：https://www.ucloud.cn/yun/72426.html

247. Strobogrammatic Number II

摘要：题目链接这题和都可以做，一种思路就是从中间开始往两边延伸，每次有种可能性和，其中开头处不能是。可以加或者用优化。 247. Strobogrammatic Number II 题目链接：https://leetcode.com/problems... 这题recursion和iteration都可以做，一种思路就是从中间开始往两边延伸，每次c[i-k], c[i+k]有5种可能性: (...

cnTomato 2019-08-14 17:29 评论0 收藏0
246. 247. 248. Strobogrammatic Number I II II

摘要：题目解答题目解答先考虑最底层的两种情况，当和当的时候，就是最中间的数为空还是存在唯一的一个数。然后我们在这个基础上，用循环两个数两个数地一起向外扩张。扩张后的结果存在里，作为再服务于上一层的扩张，得到最终结果。 246.Strobogrammatic NumberI题目：A strobogrammatic number is a number that looks the same w...

Fundebug 2019-08-14 16:31 评论0 收藏0
[Leetcode] Strobogrammatic Number 对称数

摘要：比如，先判断和是有映射的，然后和自己又是映射，所以是对称数。这样每次从中间插入两个对称的字符，之前插入的就被挤到两边去了。只插入一个字符时不能插入和插入字符和它的对应字符 Strobogrammatic Number I A strobogrammatic number is a number that looks the same when rotated 180 degrees ...

wendux 2019-08-14 12:34 评论0 收藏0
[LeetCode] 246. Strobogrammatic Number

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 represent...

whatsns 2019-08-19 11:14 评论0 收藏0
[LeetCode] 248. Strobogrammatic Number III

Problem 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 o...

yzd 2019-08-16 13:50 评论0 收藏0