LeetCode 1680: Concatenation of Consecutive Binary Numbers Solution

Master LeetCode problem 1680 (Concatenation of Consecutive Binary Numbers), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1680. Concatenation of Consecutive Binary Numbers

Medium

Math Bit Manipulation Simulation

Problem Explanation

Explanation:

To solve this problem, we need to concatenate the binary representation of numbers from 1 to n and then convert the concatenated binary string back to decimal modulo 10^9 + 7. The key idea is to build the binary representation of each number iteratively while keeping track of the current decimal value after concatenation.

Initialize result to 0.
Iterate from 1 to n:
- Calculate the number of bits required to represent the current number.
- Shift the current result to the left by the number of bits required.
- Add the current number to the result.
- Take modulo 10^9 + 7 after each step.
Return the final result. :

Solution Code

class Solution {
    public int concatenatedBinary(int n) {
        long result = 0;
        int MOD = 1000000007;
        
        for (int i = 1; i <= n; i++) {
            int numBits = (int)(Math.log(i) / Math.log(2)) + 1;
            result = (result << numBits | i) % MOD;
        }
        
        return (int)result;
    }
}

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