(Easy) Number Complement - LeetCode

Description:

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note:

1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
2. You could assume no leading zero bit in the integer’s binary representation.

 

Example 1:

Input: 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

 

Example 2:

Input: 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

 

Accepted

113,954

Submissions

181,798

Solution:

class Solution {
    public int findComplement(int num) {
     
         //System.out.println(intToBinary(num));
        
        
        return StringtoInt(intToBinary(num)); 
    }
    
    public static String intToBinary(int num){
        
        String res = "";
        
        while(num>0){
            
            int dig = num%2; 
            
            num = num/2; 
            
            res = res + dig; 
            
        }
        
        
        StringBuffer sb = new StringBuffer(res);
        
        res = sb.reverse().toString();
        
        String out = "";
        
        for(int i = 0; i< res.length(); i++){
            if(res.charAt(i)=='1'){
                out = out+"0";
            }
            else{
                out = out +"1";
            }
        }
        
        return out; 
    }
    
    public static int StringtoInt(String s){
        
        int n = s.length()-1;
        
        int res = 0; 
        
        for(int i  = 0; i<s.length(); i++){
             res = res + (int)Math.pow(2,n) * Integer.parseInt(s.substring(i,i+1));
            n = n-1;
            
        }
        
        return res;
       
    }
    
}