Mathijs Mathijs - 1 month ago 6
C# Question

SystemNullReference while converting item from string array to int and putting them in jagged array

My code is realy simple but for some reason I get a systemnullreference and I don't know what I am doing wrong. The file that i use has is as follows:

75
95 64
17 47 82
18 35 87 10
20 04 82 47 65
19 01 23 75 03 34
88 02 77 73 07 63 67
99 65 04 28 06 16 70 92
41 41 26 56 83 40 80 70 33
41 48 72 33 47 32 37 16 94 29
53 71 44 65 25 43 91 52 97 51 14
70 11 33 28 77 73 17 78 39 68 17 57
91 71 52 38 17 14 91 43 58 50 27 29 48
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23


And here is my code:

string [] lines = System.IO.File.ReadAllLines(@"C:\Users\Mathi\Documents\project_euler\problem18.txt").ToArray();
int[][] numbers = new int[lines.Length][];


for (int i = 0; i < lines.Length; i++)
{
string[] temporary = lines[i].Split();

for (int j = 0; j < temporary.Length; j++)
{
numbers[i][j] = Convert.ToInt32(temporary[j]); <-- here is where i get error
}
}

Console.ReadKey();


I am trying to get all the numbers from the text file and put them all in a jagged array.

Thanks for the help! (i am probably stupid :P)

Answer

You need to create the inner array as well:

for (int i = 0; i < lines.Length; i++)
{
    string[] temporary = lines[i].Split();

    numbers[i] = new int[temporary.Length]; // <- Added line
    for (int j = 0; j < temporary.Length; j++)
    {
        numbers[i][j] = Convert.ToInt32(temporary[j]); <-- here is where i get error
    }
}
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