strobogrammatic-number-i

Strobogrammatic Number – LeetCode 246

Problem

Description

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.

Answer

Original

Code

class Solution {
public:
    bool isStrobogrammatic(string num) {
		if(!num.size()) return false;
		string smap = "01    9 86";
		for(int l = 0, r = num.size() - 1; l <= r; ++l, --r){
			if(num[r] != smap[num[l]-'0']) return false;
		}
		return true;
    }
};

思路

从头尾两个方向遍历，对可以形成对称结构的字符对应进行查找，依次判断即可。时间复杂度$O(n)$，空间复杂度$O(1)$。

Better

思路

还没看到更好的思路。