7. Reverse Integer

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.

class Solution {

    /**
     * @param Integer $x
     * @return Integer
     */
    function reverse($x) {
        
        $r =  (int) (strrev(trim($x,"+-")) * ($x>0?1:-1));
        
        if($r >  pow(2,31)-1 || $r < -pow(2,31)){
            return 0;
        }
        return $r;
    }
}

 

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