An Interesting Method to Generate Binary Numbers from 1 to n | GeeksforGeeks

Given a number n, write a function that generates and prints all binary numbers with decimal values from 1 to n.

Following is an interesting method that uses queue data structure to print binary numbers.
1) Create an empty queue of strings
2) Enqueue the first binary number “1″ to queue.
3) Now run a loop for generating and printing n binary numbers.
……a) Dequeue and Print the front of queue.
……b) Append “0″ at the end of front item and enqueue it.
……c) Append “1″ at the end of front item and enqueue it.

Following is C++ implementation of above algorithm.

void generatePrintBinary(int n)

{

    // Create an empty queue of strings

    queue<string> q;

    // Enqueue the first binary number

    q.push("1");

    // This loops is like BFS of a tree with 1 as root

    // 0 as left child and 1 as right child and so on

    while (n--)

    {

        // print the front of queue

        string s1 = q.front();

        q.pop();

        cout << s1 << "\n";

        string s2 = s1;  // Store s1 before changing i

        // Append "0" to s1 and enqueue it

        q.push(s1.append("0"));

        // Append "1" to s2 and enqueue it. Note that s2 contains

        // the previous front

        q.push(s2.append("1"));

    }

}

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