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
- Finding n-th number made of prime digits (2, 3, 5 and 7) only
- Smallest multiple of a given number made of digits 0 and 9 only
- Number of digits in the nth number made of given four digits
- Count of integers in a range which have even number of odd digits and odd number of even digits
- Find smallest number with given number of digits and sum of digits under given constraints
- Check whether product of digits at even places is divisible by sum of digits at odd place of a number
- Count of numbers between range having only non-zero digits whose sum of digits is N and number is divisible by M
- Maximize the given number by replacing a segment of digits with the alternate digits given
- Number formed by deleting digits such that sum of the digits becomes even and the number odd
- 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
- Find the average of k digits from the beginning and l digits from the end of the given number
- Minimum number of digits to be removed so that no two consecutive digits are same
- Largest number divisible by 90 that can be made using 0 and 5
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