# 9. Palindrome Number

## 1.問題

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LI-FKdhNGd3TxspZGRF%2F-LI-FrFih9VVyBZndU4n%2F2018072203.jpg?alt=media\&token=5e833da5-a585-47b6-82af-ad52e4ed4a1d)

## 2.想法 

* 第一種作法是轉到字串後, 從頭尾兩側向前比對
* 第二種作法是轉到字串後, 反轉字串並比對兩字串

## 3.程式碼

* 第一種作法

```
class Solution {
public:
    bool isPalindrome(int x) {
        if (x < 0) {
            return false;
        }
        string str = to_string(x);
        for (int i = 0; i < str.size(); i++) {
            if (str[i] != str[str.size() - 1 - i]){
                return false;
            }
        }
        return true;
    }
};
```

* 第二種作法

```
class Solution {
public:
    bool isPalindrome(int x) {
        string s=to_string(x);
        string ori=s;
        reverse(s.begin(),s.end());
        return s==ori;
    }
};
```

## 4.Performance

* 第一種作法

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LI-FKdhNGd3TxspZGRF%2F-LI-HCv59ajKZzf7MXjO%2F2018072205.jpg?alt=media\&token=be2bb5c8-2ee8-4a7e-a154-3750d68b10bf)

* 第二種作法

![](https://901207480-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LGKoChvN9am4__HCIRK%2F-LI-FKdhNGd3TxspZGRF%2F-LI-Gz2nI4mWjmd9_h7Q%2F2018072204.jpg?alt=media\&token=f65ac743-7b2b-4541-8b65-d56f02d0a331)