Summary - Arrays
- C# course
- Beginner
- Lesson 58/116
- 5 min
Use single-dimensional and matrix arrays to write a grade table.
Summary - Arrays
In this group you learned one-dimensional arrays, index access, .Length, the int[,] matrix and the int[][] jagged array. Now you will combine them to write a grade table.
Across two exercises you will first walk a grades array with for and print each grade, then read a specific cell from a two-row matrix. One-dimensional and multi-dimensional arrays appear side by side here.
Practice Print grades with for
Declare a grades array with the value { 70, 85, 90 }. Use the pattern for (int i = 0; i < grades.Length; i++) to print each element with Console.WriteLine(grades[i]). The output should be 70, 85, 90.
Starter code
using System;
class Program
{
static void Main()
{
// Write the grades loop here
}
}Sample solution
using System;
class Program
{
static void Main()
{
int[] grades = { 70, 85, 90 };
for (int i = 0; i < grades.Length; i++)
{
Console.WriteLine(grades[i]);
}
}
}Expected output
70 85 90
Practice Read a cell from the matrix
Declare a table matrix with the value { { 1, 2, 3 }, { 4, 5, 6 } }. Print table[0, 1] with Console.WriteLine. The output should be 2.
Starter code
using System;
class Program
{
static void Main()
{
// Declare the matrix and print a cell
}
}Sample solution
using System;
class Program
{
static void Main()
{
int[,] table = { { 1, 2, 3 }, { 4, 5, 6 } };
Console.WriteLine(table[0, 1]);
}
}Expected output
2
The arrays side by side
You now know three array types: the one-dimensional int[], the matrix int[,] and the jagged int[][]. Which one to pick depends on the shape of the data.
For one-dimensional ordered data use int[]; for row-and-column data int[,]; for rows of different sizes int[][]. Use .Length and GetLength to safely check bounds.
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 With int[] nums = {10, 20, 30}; which safely accesses the last element?
int[] nums = {10, 20, 30};
Console.WriteLine(nums[?]);- nums[3]
- nums[nums.Length]
- nums[2]
- nums[nums.Length - 1] Correct answer
Explanation: nums.Length - 1 always gives the last index; it works even if the size changes.
2 Complete the last-element access
int[] nums = {1, 2, 3, 4};
int last = nums[nums.____ - 1];int[] nums = {1, 2, 3, 4};
int last = nums[nums.Length - 1];Explanation: nums.Length - 1 always gives the last index.