Print all n-digit strictly increasing numbers - GeeksforGeeks

Print all n-digit strictly increasing numbers - GeeksforGeeks
Given number of digits n in a number, print all n-digit numbers whose digits are strictly increasing from left to right.

The idea is to use recursion. We start from the leftmost position of a possible N-digit number and fill it from set of all digits greater than its previous digit. i.e. fill current position with digits (i to 9] where i is its previous digit. After filling current position, we recurse for next position with strictly increasing numbers.

void findStrictlyIncreasingNum(int start, string out, int n)

{

    // If number becomes N-digit, print it

    if (n == 0)

    {

        cout << out << " ";

        return;

    }

 

    // start from (prev digit + 1) till 9

    for (int i = start; i <= 9; i++)

    {

        // append current digit to number

        string str = out + to_string(i);

 

        // recurse for next digit

        findStrictlyIncreasingNum(i + 1, str, n - 1);

    }

}

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