Binary Number with Alternating Bits LeetCode Solution - The Coding Shala

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

Binary Number with Alternating Bits Problem

Given a positive integer, check whether it has alternating bits: namely if two adjacent bits will always have different values.

Example 1:
Input: n = 5
Output: true
Explanation: The binary representation of 5 is: 101

Example 2:
Input: n = 7
Output: false
Explanation: The binary representation of 7 is: 111.

LeetCode - Binary Number with Alternating Bits Java Solution

Approach 1

Compare alternate bits.

Java Program: 

class Solution {
    public boolean hasAlternatingBits(int n) {
        int i = 31;
        //find first 1 bit from left side
        while(((n >> i) & 1) == 0) i--;
        
        int prevBit = (n>>i) & 1;
        i--;
        while(i >= 0) {
            int currBit = (n >> i) & 1;
            if(currBit == prevBit) return false;
            prevBit = currBit;
            i--;
        }
        return true;
    }
}

Approach 2

Divide by two.

Java Program: 

class Solution {
    public boolean hasAlternatingBits(int n) {
        int prevBit = n%2;
        n /= 2;
        while(n > 0) {
            int currBit = n%2;
            if(currBit == prevBit) return false;
            prevBit = currBit;
            n /= 2;
        }
        return true;
    }
}


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