# Posts tagged as “easy”

Given an integer n. No-Zero integer is a positive integer which doesn’t contain any 0 in its decimal representation.

Return a list of two integers [A, B] where:

• A and B are No-Zero integers.
• A + B = n

It’s guarateed that there is at least one valid solution. If there are many valid solutions you can return any of them.

Example 1:

Example 2:

Example 3:

Example 4:

Example 5:

Constraints:

• 2 <= n <= 10^4

## Solution: Brute Force

Time complexity: O(nlogn)
Space complexity: O(1)

## C++

We are given a list nums of integers representing a list compressed with run-length encoding.

Consider each adjacent pair of elements [a, b] = [nums[2*i], nums[2*i+1]] (with i >= 0).  For each such pair, there are a elements with value b in the decompressed list.

Return the decompressed list.

Example 1:

Input: nums = [1,2,3,4]
Output: [2,4,4,4]


Constraints:

• 2 <= nums.length <= 100
• nums.length % 2 == 0
• 1 <= nums[i] <= 100

## Solution: Simulation

Time complexity: O(sum(n_i))
Space complexity: O(sum(n_i)) or O(1)

## C++

Given an integer n, return any array containing n unique integers such that they add up to 0.

Example 1:

Input: n = 5
Output: [-7,-1,1,3,4]
Explanation: These arrays also are accepted [-5,-1,1,2,3] , [-3,-1,2,-2,4].


Example 2:

Input: n = 3
Output: [-1,0,1]


Example 3:

Input: n = 1
Output: [0]


Constraints:

• 1 <= n <= 1000

## Solution: Generation

Use numbers from {-n/2, … n/2} + {0 if n is odd}

Time complexity: O(n)
Space complexity: O(1)

## C++

Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.

After doing so, return the array.

Example 1:

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]

Constraints:

• 1 <= arr.length <= 10^4
• 1 <= arr[i] <= 10^5

## Solution: Scan from right to left

Time complexity: O(n)
Space complexity: O(1)

## C++

Given an array nums of integers, return how many of them contain an even number of digits.

Example 1:

Input: nums = [12,345,2,6,7896]
Output: 2
Explanation:
12 contains 2 digits (even number of digits).
345 contains 3 digits (odd number of digits).
2 contains 1 digit (odd number of digits).
6 contains 1 digit (odd number of digits).
7896 contains 4 digits (even number of digits).
Therefore only 12 and 7896 contain an even number of digits.


Example 2:

Input: nums = [555,901,482,1771]
Output: 1
Explanation:
Only 1771 contains an even number of digits.


Constraints:

• 1 <= nums.length <= 500
• 1 <= nums[i] <= 10^5

## Solution: Math

Time complexity: O(n * log(max(num)))
Space complexity: O(1)

## Python3

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