Leetcode_7_Reverse Integer, leetcode_7_reverse

Leetcode_7_Reverse Integer, leetcode_7_reverse
Description:

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 shoshould 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 can 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.

Ideas:

The idea is concise and clear. Store the unsigned parts of integers in an array and assemble them into a new integer. Of course, overflow and symbols all need to be considered.

Code:

int reverse(int x) {        int i=0;        int num[20]={0};        long sum=0;        int flag=0;        if(x<0)            {x=-x;flag=1;}        while(x!=0)        {            num[i++]=x%10;            x/=10;        }        for(int j=0;j<i;j++)        {            sum=sum*10+num[j];        }        if(flag)        sum=-sum;        return sum;            }

Result: