LeetCode Reverse Integer

Reverse Integer

Total Accepted:2839Total Submissions:6946My Submissions

Reverse digits of an integer.

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

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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?

Throw an exception? Good, but what if throwing an exception is not an option? You would then have to re-design the function (ie, add an extra parameter).

很简单，不多说。

最笨的方法如下：

public int reverse(int x) {
		int temp=x,index=0;
		boolean flag;
		if(temp>=0)
			flag=true;
		else{
			flag=false;
			temp=Math.abs(x);
		}
		while(temp!=0){
			temp=temp/10;
			index++;
		}
		int sum=0;
		for(int i=1;i<=index;i++){
			temp=Math.abs(x);
			for(int j=0;j<index-i;j++)
				temp=temp/10;
			sum+=(temp%10)*Math.pow(10,i-1);
		}
		if(flag)
			return sum;
		else
			return -1*sum;
    }

比较常用的方法如下：

public static int reverse2(int x) {
		boolean flag;
		if(x>=0)
			flag=true;
		else
			flag=false;
		int sum=0,temp=Math.abs(x);
		while(temp!=0){
			sum*=10;
			sum+=temp%10;
			temp/=10;
		}
		if(flag)
			return sum;
		else
			return -1*sum;
    }