Strobogrammatic Number -- LeetCode

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.

思路：写一个rotate函数，输入是0-9，输出是旋转后的数字。若旋转后不是数字，则输出一个'X'。

在主函数中，我们要检查的数字是string类型，用left和right两个指针从两端向中间逐个比较。用roate函数计算left所指的数字旋转后的结果并与right所指的数字进行比较。若不相同则为false。

class Solution {
public:
    char rotate(char c) {
        if (c == '6')
            return '9';
        else if (c == '9')
            return '6';
        else if (c == '0' || c == '1' || c == '8')
            return c;
        else return 'X';
    }
    bool isStrobogrammatic(string num) {
        int left = 0, right = num.size() - 1;
        while (left <= right) {
            if (rotate(num[left]) != num[right])
                return false;
            left++;
            right--;
        }
        return true;
    }
};