Mastering Arrays in C# for Coding Interviews

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? Arrays in C# — A Practical Guide for Interview Preparation


Arrays are one of the most fundamental data structures used in programming and appear frequently in coding interviews.

What is an Array?


An array is a fixed-size, indexed collection of elements of the same type.

Declaring & Initializing Arrays


// Declare and allocate memory
int[] numbers = new int[5];

// Declare and assign values
int[] scores = new int[] { 90, 85, 78, 92, 88 };

// Short-hand initialization
string[] names = { "Alice", "Bob", "Charlie" };
? Accessing and Updating Elements


int first = scores[0];
scores[2] = 80;
int last = scores[scores.Length - 1];
? Looping Through Arrays


// Using for loop
for (int i = 0; i < scores.Length; i++) {
Console.WriteLine(scores);
}

// Using foreach loop
foreach (int score in scores) {
Console.WriteLine(score);
}
? Useful Array Operations


Array.Sort(scores); // Sort ascending
Array.Reverse(scores); // Reverse array
int index = Array.IndexOf(scores, 92); // Find index of 92
? Common Use Cases

Use Case	Description
Fixed-size data storage	e.g., Top 5 student scores
Indexed logic	Two pointers, prefix sum, etc.
Brute force comparisons	e.g., nested loops for pair matching

? Interview Example: Two Sum (Brute Force)


public int[] TwoSum(int[] nums, int target) {
for (int i = 0; i < nums.Length; i++) {
for (int j = i + 1; j < nums.Length; j++) {
if (nums + nums[j] == target)
return new int[] { i, j };
}
}
return new int[] { -1, -1 };
}
? Summary

Feature	Syntax Example
Declare	int[] arr = new int[5];
Access	arr[0], arr[arr.Length - 1]
Update	arr[2] = 100;
Loop	for or foreach
Sort/Reverse	Array.Sort(arr), Array.Reverse()

Stay tuned for the next post where we tackle HashSet and use it to solve unique element problems efficiently.

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