如何从 array1 打印 item[0] 并完成 array2 的结果（与 item[1] 重复）

Question

I have these arraies

string[] array1 = {"A","A","A","A", "B","B","C","C","C","D"};
int[] array2 = {1,2,3,4,5,6,7,8,9,10};

The expected output is:

A

• 1
• 2
• 3
• 4

B

• 5
• 6

and so on.....

I tried this

string[] array1 = { "A", "A", "A", "A", "B", "B", "C", "C", "C", "D" };

int[] array2 = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

for (int x = 0; x < array1.Length; x++)
{
    if (array1[x] == array1[x == array1.Length-1? x : x + 1])
    {
        Console.WriteLine(array1[x]);
        Console.WriteLine(array2[x]);
    }
    else
    {
        continue;
    }

}
Console.ReadKey();

But doesn't work as expected.

Answer 1

How about:

for (int x = 0; x < array1.Length; x++)
{
    // display first letter and any letter different from previous one
    if (x == 0 || array1[x] != array1[x - 1])
    {
        Console.WriteLine(array1[x]);
    }
    // in all cases, write the number
    Console.WriteLine(array2[x]);
}

Note that when doing this, you should make sure that array1.Length == array2.Length or you might end up in trouble.

Answer 2

Is this a homework assignment or a practical problem you need to solve? If the former, then your classwork may require a solution using only arrays and then the other answer is probably preferred. But if this is a practical problem, then IMHO LINQ would be a better approach, being more expressive of what you actually want to do.

For example:

string[] array1 = {"A","A","A","A", "B","B","C","C","C","D"};
int[] array2 = {1,2,3,4,5,6,7,8,9,10};
var groups = array1.Zip(array2, (x, y) => (Name: x, Value: y)).GroupBy(t => t.Name);

foreach (var group in groups)
{
    Console.WriteLine(group.Key);
    Console.WriteLine(string.Join(Environment.NewLine, group.Select(t => t.Value)));
}

The above reorganizes the data by combining the corresponding values from each array into a single tuple value, and then uses LINQ to group each value by the name.

Once this is done, outputting the information is as simple as displaying the key for each group, and then displaying all the values within each group.