Exploring Various Methods for Obtaining Subarrays in C#

What happened

Encountering the LeetCode problem #2966 “Divide Array Into Arrays With Max Difference”, I found myself needing to retrieve the next three elements from a specific index in the array to form a subarray.

During the process of writing the solution, I kept forgetting which syntax to use for this task. However, I wanted to avoid traditional methods like using a for loop to iterate through each element individually. Hence, I decided to make notes to prevent forgetting this syntax in the future.

Solution

The following examples will all use the array nums, and extract cnt elements starting from startIdx to form a subarray.

Solution 1 – for loop

int[] tmp = new int[cnt];
for (int i = 0; i < cnt; i++)
{
    tmp[i] = nums[startIdx + i];
}

The most traditional approach involves first defining the size of the array and then using a loop to individually set the index values.

Solution 2 – LINQ – SKIP、 Take

int[] tmp = nums.Skip(startIdx).Take(cnt).ToArray();

This should be one of the most familiar syntaxes for everyone developing in C#, enabling easy accomplishment in just one line.

Solution 3 – Range operator

int[] tmp = nums[startIdx..(startIdx+cnt)];

In addition to LINQ, the introduction of the Range operator in C# 8.0 has made the process even more straightforward.

The Range operator can even be combined with the ^ (end operator) for additional operations. For example: nums[startIdx..^3] extracts a subarray from the nums array starting from startIdx to the third element from the end.

Conclusion

Make a record, just in case one day I suddenly turn into a goldfish and forget everything!

If I discover other methods later, I’ll come back to update it!

I’ve been using GPT to create Japanese versions of translated articles recently, hoping to attract different users.

Reference

• Ranges and indices – C# feature specifications | Microsoft Learn
• Array slices in C# – Stack Overflow

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Some Random notes