Given a number N in the form of string. The task is to find the greatest number that has same set of digits as N and is smaller than N. If it is not possible to find any such numebr, then print “not possible”.
Input: N = "218765" Output: 218756 Input: N = "1234" Output: Not Possible Input: N = "262345" Output: 256432
Following are few observations about the greatest number smaller than N:
- If all digits sorted in ascending order, then output is always “Not Possible”. For example, 1234.
- If all digits are sorted in descending order, then we need to swap last two digits. For example, 4321.
- For other cases, we need to process the number from rightmost side (why? because we need to find the greatest of all smaller numbers).
- Traverse the given number from rightmost digit, keep traversing till you find a digit which is greater than the previously traversed digit. For example, if the input number is “262345”, we stop at 6 because 6 is greater than previous digit 5. If we do not find such a digit, then output is “Not Possible”.
- Now search the right side of above found digit ‘d’ for the greatest digit smaller than ‘d’. For “262345?, the right side of 6 contains “2345”. The greatest digit smaller than 6 is 5.
- Swap the above found two digits, we get “252346” in above example.
- Now sort all digits from position next to ‘d’ to the end of number in descending order. The number that we get after sorting is the output. For above example, we sort digits in bold 252346. We get 256432 which is the previous smaller number for input 262345.</li
Below is the implementation of the above approach:
Greatest smaller number with same set of digits is 256432
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
- Largest number smaller than or equal to n and digits in non-decreasing order
- Find the largest number smaller than integer N with maximum number of set bits
- Find the Largest number with given number of digits and sum of digits
- Find the largest number that can be formed by changing at most K digits
- Find the Largest Cube formed by Deleting minimum Digits from a number
- Largest smaller number possible using only one swap operation
- Largest number smaller than or equal to N divisible by K
- Maximize number of groups formed with size not smaller than its largest element
- Largest number with prime digits
- Largest number possible after removal of K digits
- Largest number with the given set of N digits that is divisible by 2, 3 and 5
- Largest number not greater than N all the digits of which are odd
- Find the largest multiple of 3 from array of digits | Set 2 (In O(n) time and O(1) space)
- Find smallest number with given number of digits and sum of digits under given constraints
- Largest number not greater than N which can become prime after rearranging its digits
- Find the closest and smaller tidy number
- Find the average of k digits from the beginning and l digits from the end of the given number
- Find the number of positive integers less than or equal to N that have an odd number of digits
- Find smallest number formed by inverting digits of given number N
- Find smallest possible Number from a given large Number with same count of digits
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.