力扣476（数字的补数）

力扣数字的补数链接

题解：

class Solution {

    /**
     * @param Integer $num
     * @return Integer
     */
    function findComplement($num) {
        if($num==1){
            return 0;
        }
        $binNum = $this->toBin($num);
        $rev = $this->toRev($binNum);
        $result = 0;
        $len = strlen($rev);
        for($j = $len -1 ; $j>=0;$j-- ){
            if(substr($rev,$j,1)==1){
                $result+= pow(2,$len-$j-1);
            }
        }
        return $result;
    }

    private function toBin($nums){
        if($nums==0 || $nums == 1){
            return $nums;
        }
        $divisor = intval($nums/2);
        $binNum = intval($nums%2);
        return $binNum.$this->toBin($divisor);
    }

    private function toRev($binNum){
        $rev='';
        $binNum = strrev($binNum);
        for($i = 0 ; $i<strlen($binNum);$i++){
            if(substr($binNum,$i,1)==1){
                $rev.='0';
            }else{
                $rev.='1';
            }
        }
        return $rev;
    }
}