Educational Codeforces Round 40 (Rated for Div. 2) B. String Typing
2023. Number of Pairs of Strings With Concatenation Equal to Target
Given an array of digit strings nums and a digit string target, return the number of pairs of indices (i, j) (where i != j) such that the concatenation of nums[i] + nums[j] equals target.
An array nums of length n is beautiful if:
- nums is a permutation of the integers in the range [1, n].
- For every 0 <= i < j < n, there is no index k with i < k < j where 2 * nums[k] == nums[i] + nums[j].
Given the integer n, return any beautiful array nums of length n. There will be at least one valid answer for the given n.
2033. Minimum Operations to Make a Uni-Value Grid
You are given a 2D integer grid of size m x n and an integer x. In one operation, you can add x to or subtract x from any element in the grid.
A uni-value grid is a grid where all the elements of it are equal.
Return the minimum number of operations to make the grid uni-value. If it is not possible, return -1.
Given a 2D integer array nums, return all elements of nums in diagonal order as shown in the below images.
825. Friends Of Appropriate Ages
There are n persons on a social media website. You are given an integer array ages where ages[i] is the age of the ith person.
A Person x will not send a friend request to a person y (x != y) if any of the following conditions is true:
- age[y] <= 0.5 * age[x] + 7
- age[y] > age[x]
- age[y] > 100 && age[x] < 100
Otherwise, x will send a friend request to y.
Note that if x sends a request to y, y will not necessarily send a request to x. Also, a person will not send a friend request to themself.
Return the total number of friend requests made.