Number Complement LeetCode Solution - The Coding Shala

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 In this post, we will learn how to solve LeetCode's Number Complement Problem and will implement its solution in Java.

Number Complement Problem

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

Example 1:
Input: num = 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.

Practice this problem on LeetCode.

LeetCode - Number Complement Java Solution

Approach 1

Just flip the bit and make decimal value from it.

Java Program: 

class Solution {
    public int findComplement(int num) {
        int ans = 0;
        int two = 1;
        while(num > 0) {
            //if bit is 0 then flip and make binary of result
            if(num%2 == 0) {
                ans += two;
            }
            two *= 2;
            num /= 2;
        }
        return ans;
    }
}

Approach 2

Using bit Manipulation.

Java Program: 

class Solution {
    public int findComplement(int num) {
        int ans = 0;
        int i = 31;
        //find first 1 from left
        while(num >> i == 0) i--;
        while(i >= 0) {
            //flip the bit
            if(((num >> i) & 1) == 0) {
                ans |= 1 << i;
            }
            i--;
        }
        return ans;
    }
}


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