LeetCode_Reverse Integer

Reverse Integer

 

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Have you thought about this?

Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!

If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.

Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows. How should you handle such cases?

For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Update (2014-11-10):
Test cases had been added to test the overflow behavior.

題目要求實現對一個int類型的數字進行翻轉，需要注意的是翻轉之後的數字可能出現越界（經過測試，如果越界，系統希望輸出數字0，不越界則正常輸出）

java解題：

public int reverse(int x) {
       long result = 0;  //這裏要聲明long型的，因爲該數在不斷計算過程中可能超過int的範圍
        while (x != 0) {  
            result = result * 10 + x % 10; //最重要的邏輯
            if(result>Integer.MAX_VALUE || result<Integer.MIN_VALUE)//加上越界判斷
            	return 0;
            x = x / 10;   
        }  
        return (int) result; //注意類型轉換
	}