Given an integer N, the task is to find the Nth number made up of odd digits (1, 3, 5, 7, 9) only.
First few numbers made up of odd digits are 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 31, …
Input: N = 7
1, 3, 5, 7, 9, 11, 13
13 is the 7th number in the series
Input: N = 10
Approach 1 (Simple) : Starting from 1, keep checking if the number is made up of only odd digits (1, 3, 5, 7, 9) and stop when nth such number is found.
Below is the implementation of the above approach:
Approach 2 (Queue Based): The idea is to generate all numbers (smaller than n) containing odd digits only. How to generate all numbers smaller than n with odd digits? We use queue for this. Initially we push ‘1’, ‘3’, ‘5’, ‘7’ and ‘9’ to the queue. Then we run a loop while count of processed elements is smaller than n. We pop an item one by one and for every popped item x, we generate next numbers x*10 + 1, x*10 + 3, x*10 + 5, x*10 + 7 and x*10 + 9. We enqueue these new numbers. Time complexity of this approach is O(n)
Please refer below post for implementation of this approach.
Count of Binary Digit numbers smaller than N
- Find the n-th number made of even digits only
- Smallest multiple of a given number made of digits 0 and 9 only
- Finding n-th number made of prime digits (2, 3, 5 and 7) only
- Number of digits in the nth number made of given four digits
- Largest number divisible by 90 that can be made using 0 and 5
- Check whether product of digits at even places is divisible by sum of digits at odd place of a number
- Find position of the given number among the numbers made of 4 and 7
- Total number of different staircase that can made from N boxes
- Count of numbers between range having only non-zero digits whose sum of digits is N and number is divisible by M
- Check whether the number can be made perfect square after adding 1
- Find smallest number with given number of digits and sum of digits
- Find the Largest number with given number of digits and sum of digits
- Minimum number of digits to be removed so that no two consecutive digits are same
- Smallest number with given sum of digits and sum of square of digits
- Print a number strictly less than a given number such that all its digits are distinct.
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