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I have a problem with the following task from the platform Codesignal:

After some investigation, you've created a database containing a foreignCompetitors table, which has the following structure:

competitor: the name of the competitor; country: the country in which the competitor is operating. In your report, you need to include the number of competitors per country and an additional row at the bottom that contains a summary: ("Total:", total_number_of_competitors)

Given the foreignCompetitors table, compose the resulting table with two columns: country and competitors. The first column should contain the country name, and the second column should contain the number of competitors in this country. The table should be sorted by the country names in ascending order. In addition, it should have an extra row at the bottom with the summary, as described above.

Example

For the following table foreignCompetitors

my solution:

I couldn't figure out why I passed 22/23 on this challenge and not able to solve the last test case since it was hidden.. The feedback from the CodeSignal is

Tests passed: 22/23. Execution time limit exceeded: Program exceeded the execution time limit. Make sure that it completes execution in a few seconds for any possible input.

Challenge Given an array a that contains only numbers in the range from 1 to a.length, find the first duplicate number for which the second occurrence has the minimal index. In other words, if there are more than 1 duplicated numbers, return the number for which the second occurrence has a smaller index than the second occurrence of the other number does. If there are no such elements, return -1.

Example

For a = [2, 1, 3, 5, 3, 2], the output should be solution(a) = 3.

There are 2 duplicates: numbers 2 and 3. The second occurrence of 3 has a smaller index than the second occurrence of 2 does, so the answer is 3.

For a = [2, 2], the output should be solution(a) = 2; For a = [2, 4, 3, 5, 1], the output should be solution(a) = -1.

Input/Output

[execution time limit] 4 seconds (js)

[input] array.integer a

Guaranteed constraints: 1 ≤ a.length ≤ 105, 1 ≤ a[i] ≤ a.length.

[output] integer

The element in a that occurs in the array more than once and has the minimal index for its second occurrence. If there are no such elements, return -1.

My code

I am trying to call/print the following linked list:

I'm asked to check whether a given string can be a palindrome after rearranging and then return true if it can be a palindrome or false if it cannot be a palindrome.

I'm getting a runtime error: Segmentation fault while running tests.

Here's my code:

so Im working on a codesignal problem, and these are the instructions:

I'm having this issue where my .map won't update any of my data when it rerenders. I have a simple player that is moving to the next element in the playlist array and after its updated or every time I click next or prev in my Playerbar it supposed to show Artist of the selected song {artist.name} and the Selected song {song.name} but for some reason nothing changes. I think I have missed something obvious but can't see it Can someone help me out please? Thanks.

I am working through some problems on CodeSignal. I came across this one, arrayMaxConsecutiveSum. I got it to pass almost all tests, but it is timing out on the last one. If I move the test into custom tests, it passes there, so I'm not sure what to do. How do I code it better so that it doesn't time out?

Problem:

Given array of integers, find the maximal possible sum of some of its k consecutive elements.
Example:
For inputArray = [2, 3, 5, 1, 6] and k = 2, the output should be arrayMaxConsecutiveSum(inputArray, k) = 8. All possible sums of 2 consecutive elements are:
2 + 3 = 5;
3 + 5 = 8;
5 + 1 = 6;
1 + 6 = 7.
Thus, the answer is 8.

EDIT: So I changed my code to the following:

I took a practice CodeSignal exam and was able to pass 14/16 test cases for this problem. You are given a vector as input (list of ints) and the solution will be long long.

Originally I simply used a brute-force solution of two for loops and adding the current a[i] concat a[j] to a running total. However, I tried to optimize this by using memoization. I used a unordered_map of pairs to check if I already computed the (i,j) pair and if so, simply return the cached result. Even with my optimization, I still don't pass any additional test cases and receive a 14/16 result. What insight or optimizations am I missing?

I have found similar online problems, however their insight doesn't seem to be applicable to this specific problem.

Ex: Similar Problem

Question:

Given an array of positive integers a, your task is to calculate the sum of every possible concat(a[i], a[j]), where concat(a[i],a[j]) is the concatenation of the string representations of a[I] and a[j] respectively.

Ex: