How does this nested loop output a list separated into 3 sections with 3 words in each section?-CodePudding

I'm very new to C#. I was curious on how this block of code printed out 3 separate lines with the 3 words in the arrays. Could someone explain how it works?

using System;

namespace MyFirstProgram
{
    class Program 
    {
        static void Main(string[] args)
        {

            String[,] parkingLot = {{ "Mustang", "F-150", "Explorer" }, { "Corvette", "Camaro", "Silverado" }, { "Corolla", "Camry", "Rav4" }};

            for(int i = 0; i < parkingLot.GetLength(0); i  )
            {
                for (int j = 0; j < parkingLot.GetLength(1); j  )
                {
                    Console.Write(parkingLot[i, j]   " ");
                }
                Console.WriteLine();
            }

            Console.ReadKey();
        }
    }
}```

CodePudding user response：

The GetLength() method returns the size of the dimension passed in:

Gets a 32-bit integer that represents the number of elements in the specified dimension of the Array.

Notice the first call gets passed a zero:

parkingLot.GetLength(0)

This returns the number of ROWS in the 2D array.

The second call is passed a one:

parkingLot.GetLength(1)

Which tells you the number of COLUMNS in the 2D array.

Perhaps this example will illustrate the concept better:

String[,] parkingLot = {
  { "a", "b", "c" },
  { "1", "2", "3" },
  { "red", "green", "blue" },
  { "cat", "dog", "fish"},
  { "A1", "B2", "C3"}
};

for(int row = 0; row < parkingLot.GetLength(0); row  ) // 5 rows
{
  for (int col = 0; col < parkingLot.GetLength(1); col  ) // 3 columns
  {
    Console.Write(parkingLot[row, col]   " ");
  }
  Console.WriteLine();
}

Output:

a b c 
1 2 3 
red green blue 
cat dog fish 
A1 B2 C3

CodePudding user response：

I'm going to break this down into each line of the code, and explain what it does.

String[,] parkingLot = { { "Mustang", "F-150", "Explorer" }, { "Corvette", "Camaro", "Silverado" }, { "Corolla", "Camry", "Rav4" } };

parkingLot is a multi-dimensional string Array. This means this is a string array that hold other arrays of type string. Think of each {} within the bigger {} its own Array object that can be accessed.

for (int i = 0; i < parkingLot.GetLength(0); i  )

For loops are designed to loop through a specified number of elements. the integer "i" created at the start indicates that the loop will start at index 0. We start at 0 because array indexing starts at 0.

The duration of this loop lasts as long as the number of arrays ({}) in the initialised array. In this case, because parkingLot contains 3 arrays, the length is 3.

for (int j = 0; j < parkingLot.GetLength(1); j  )

This part of the code iterates within the for-loop above it, and iterates over every element inside a single array. The "GetLength(1)" part of the code grabs the length of a single array instance within the overall array. For example: the first array instance in this multi-dimensions array contains { "Mustang", "F-150", "Explorer" }, being 3 strings. Therefore, the length will also be 3.

Console.Write(parkingLot[i, j]   " ");

Here, we can see that there's a reference to i and j. Let me show you what happens step by step:

when i=0, the code begins to iterate another loop, which must compute j = 0, j = 1 and j = 2 before moving to i = 1. This means that it must read every element in the array before moving to the next array.

For Example: say:

i = 0, and j = 0. this would be accessing "Mustang"
i = 1, and j = 2 would be accessing "Silverado"
i = 2 and j = 1 would be accessing "Camry"

Console.WriteLine();

After writing each element in the j loop, this piece of code writes the responses to the console. That's why each elements of arrays appear on one line.

Console.ReadKey();

After you press this key, the program closes.

I suggest you play around with the variables and create your own arrays and multi-dimensional arrays. That way you can see how they operate and what they don't like you doing with them.