Array

Array #

Array is a data structure that stores a fixed-size sequential collection of elements of the same type.


You can declare an array with the following syntaxs.

The compiler determines the size of the array if you do not specify the size.

string[] weekdays = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};
int[] arr = new int[5];
arr[0] = 10;

Console.WriteLine(weekdays[1]); // output: Tue
Console.WriteLine(arr[0]); // output: 10

You can use multi-dimensional arrays by using commas to separate the dimensions.

Accessing elements of multi-dimensional array works in the following way.

It looks different from other programming languages.

You need to focus on the form of map[i,j].

char[,] map = {
    {'.', '.', 'E'},
    {'.', '#', '.'},
    {'S', '#', '#'},
};

for (int i = 0; i < map.GetLength(dimension:0); i++) {
    for (int j = 0; j < map.GetLength(dimension:1); j++) {
        Console.Write($"{map[i, j]}");
    }
    Console.WriteLine();
}

// Output:
// . . E
// . # .
// S # #

You cannot use map[i][j] to access elements of multi-dimensional array. 

char[,] map = {
    {'.', '.', 'E'},
    {'.', '#', '.'},
    {'S', '#', '#'},
};

// ❌ compile error
map[0][0] = 'X';

A jagged array is an array whose elements are themselves arrays.

Jagged arrays are similar to multi-dimensional arrays, but the sizes of the inner arrays can vary.

char[][] map = new char[2][];
map[0] = new char[] { 'H', 'e', 'l', 'l', 'o' };
map[1] = new char[] { 'W', 'o', 'r', 'l', 'd' };

map[0][4] = 'O';

// Output: HellO
Console.WriteLine(string.Join("", map[0]));

System.Linq namespace provides various useful Methods for arrays. 

using System.Linq;

int[] arr = {1,4,7,3,2,4,1};

Console.WriteLine($"sum: {arr.Sum()}"); // 22
Console.WriteLine($"avg: {arr.Average()}"); // 3.1428..
Console.WriteLine($"min: {arr.Min()}"); // 1
Console.WriteLine($"max: {arr.Max()}"); // 7

// slice 처럼 이용
// output: 7 3 
Console.WriteLine(string.Join(" ", arr.Skip(2).Take(2).ToList()));

Fill an array with a specific value. 

int[] arr = new int[5];
Array.Fill(arr, int.MaxValue);
// output: 2147483647 2147483647 2147483647 2147483647 2147483647
Console.WriteLine(string.Join(" ", arr));

or

var arr = Enumerable.Repeat(int.MaxValue, 5).ToArray();
Console.WriteLine(string.Join(" ", arr));