題目

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows

題意

輸入一個32位整數，要求逆序輸出。

分析

樣例1、2正常逆序輸出；

樣例3輸入數字末尾帶0，逆序輸出時應當捨去0。

*if(!x) 表示條件為0執行語句，while(x)表示持續執行直到x=0。

*先將int型轉換成longlong型，最後判斷是否溢位。

程式碼

class Solution {
public:
    int reverse(int x) {
        if(!x)  return 0;
        while(x % 10 == 0)    x /= 10;
        long long sum = 0;
        while(x) {
            sum = sum * 10 + x % 10;
            x /= 10;
        }
        int numb = sum;
        if(numb == sum)  return numb;
        else return 0;
    }
};
 

待解

class Solution {public:}含義？