74 lines
2.5 KiB
Markdown
Executable File
74 lines
2.5 KiB
Markdown
Executable File
---
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layout: post
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title: Leetcode - Concatenation of array(1929)
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date: '2022-11-19 08:43:07 +0800'
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categories: [Code, C]
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tags: [c, leetcode] # TAG names should always be lowercase
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author: devoalda
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math: true
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libraries:
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- mathjax
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math: true
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---
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# Introduction
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Given an integer array nums of length n, you want to create an array ans of length 2n where ans[i] == nums[i] and ans[i + n] == nums[i] for 0 <= i < n (0-indexed).
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Specifically, ans is the concatenation of two nums arrays.
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Return the array ans.
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## Example
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```shell
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Input: nums = [1,2,1]
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Output: [1,2,1,1,2,1]
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Explanation: The array ans is formed as follows:
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- ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]]
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- ans = [1,2,1,1,2,1]
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```
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# Process
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This was a pretty simple one other that figuring out how to use `malloc` again. This would be much simpler to do in python.
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After creating an array with size dynamically allocated to `2n` where `n` is the size of the input array, I've managd to follow the description and concatenate the array using a for loop.
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There should probably be a more elegant and efficient way to do this, but I'll still need to learn more about pointers and arrays.
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# Code
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```c
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/**
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* Note: The returned array must be malloced, assume caller calls free().
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*/
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int* getConcatenation(int* nums, int numsSize, int* returnSize){
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//int n = (sizeof(nums)/sizeof(int));
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int *ans = (int *)malloc(2 * numsSize * sizeof(int));
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int i;
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for (i = 0; i<numsSize; i++){
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ans[i] = nums[i];
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ans[i+numsSize] = nums[i];
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}
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*returnSize = 2 * numsSize;
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return ans;
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}
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```
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{: file="Concatenation of array.c" }
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# Afterthoughts
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1. I initially thought of getting the size "dynamically" by using `sizeof(nums)/sizeof(int)` but I instead realize that I should just use the input parameter `numsSize` instead. However, I'm leaving it in the code as a comment for future reference.
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2. I also had trouble with the second perimeter of the for loop, I used `i+2*numsSize` but I realized that I should just use `numsSize` instead as I didn't really have to loop through an empty array towards the end. So, looping through the array once with `i<numsSize` is enough to insert the values in position `i` and `i+numsSize`.
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3. I didn't know that I should use all the input parameters and had a _heap buffer overflow error_ until I added the `*returnSize = 2 * numsSize;` line as it is used to return the size of the array.
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I'm still pretty new to the leetcode ecosystem and have to do more practices to truly understand the proper way of attempting the questions.
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