How many four-digit positive integers are there that have the digit 1? attempt: There are $9000$ numbers that contains $4$ digits. the largest, most trusted The task is to find the smallest and largest palindromic number possible with N digits. Input: N = 4 Output: Smallest Palindrome = 1001 Largest Palindrome = 9999 Input: N = 5 Output: Smallest Palindrome = 10001 Largest Palindrome = 99999. Smallest N-digit Palindromic Number: On observing carefully, you will observe that for N = 1, the smallest To form the largest 4-digit number by using the given set of numbers, provided only one number can be used twice, we repeat the largest number twice and arrange the given numbers in descending order. Thousands Hundreds Tens Ones 9 9 2 0 ∴ 9, 920 is the largest 4-digit number formed. Hence, the sum of the largest and the smallest numbers 432 7236 9546. Time complexity :- O(N^2) Space complexity :- O(1) Approach 2 (Efficient) : We will scan the number from backward direction. In the scan, if the ith digit is the largest by far, store it and its index or if the current digit is smaller than the largest digit recorded by far, this digit and the largest digit are the best suitable for swap. .

4 digit largest number