Reverse Integer

Reverse digits of an integer. For example: x = 123, return 321.

Example Questions Candidate Might Ask:

• Q: What about negative integers?
• A: For input x = –123, you should return –321.
• Q: What if the integer’s last digit is 0? For example, x = 10, 100, …
• A: Ignore the leading 0 digits of the reversed integer. 10 and 100 are both reversed as 1.
• Q: What if the reversed integer overflows? For example, input x = 1000000003.
• A: In this case, your function should return 0.

Discussion

比较简单，注意细节。容易漏掉判断溢出。

Solution

class Solution {
public:
    /**
     * @param n the integer to be reversed
     * @return the reversed integer
     */
    int reverseInteger(int n) {
        // Write your code here
        int result = 0;
        while(n!=0) {
            if(abs(result) > INT_MAX/10) return 0;//判断溢出
            result = result*10 + n%10;
            n /=10;
        }
        return result;
    }
};

int reverseInteger(int n) {
        long long result = 0;
        unsigned int temp = abs(n);
        while (temp > 0) {
            result *= 10;
            result += temp % 10;
            temp /= 10;
        }
        result = (n >= 0) ? result : -result;
        result = (result > INT_MAX || result < INT_MIN) ? 0 : result;
        return result;
    }