Zip operation in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to zip two integer arrays and print the pairs.

C Sharp (C#)

var numbers = new[] {1, 2, 3};
var words = new[] {"one", "two", "three"};
var zipped = numbers.[1](words, (n, w) => (n, w));
foreach (var (n, w) in zipped)
{
    Console.WriteLine($"{n} - {w}");
}

Drag options to blanks, or click blank then click option'

AZip

BSelect

CWhere

DOrderBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select instead of Zip will not combine two sequences.

Where filters elements but does not combine sequences.

The Zip method combines two sequences element-wise into pairs.

2fill in blank

medium

Complete the code to zip two lists and create a dictionary from the pairs.

C Sharp (C#)

var keys = new List<string> {"a", "b", "c"};
var values = new List<int> {1, 2, 3};
var dict = keys.[1](values, (k, v) => new { k, v })
               .ToDictionary(x => x.k, x => x.v);

Drag options to blanks, or click blank then click option'

AGroupBy

BZip

CSelect

DOrderBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select only projects one sequence, not combining two.

GroupBy groups elements but does not pair two sequences.

Zip pairs elements from two sequences, which can then be converted to a dictionary.

3fill in blank

hard

Fix the error in the code to correctly zip two arrays and print the sum of pairs.

C Sharp (C#)

int[] arr1 = {1, 2, 3};
int[] arr2 = {4, 5, 6};
var result = arr1.[1](arr2, (x, y) => x + y);
foreach (var sum in result)
{
    Console.WriteLine(sum);
}

Drag options to blanks, or click blank then click option'

AJoin

BSelect

CConcat

DZip

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select only works on one sequence.

Concat joins sequences end to end, not element-wise.

Zip combines two sequences element-wise, allowing you to sum pairs.

4fill in blank

hard

Fill both blanks to create a zipped list of tuples from two arrays and print them.

C Sharp (C#)

string[] fruits = {"apple", "banana", "cherry"};
int[] counts = {5, 3, 7};
var zipped = fruits.[1](counts, ([2] f, c) => (f, c));
foreach (var (f, c) in zipped)
{
    Console.WriteLine($"{f} has {c} items");
}

Drag options to blanks, or click blank then click option'

AZip

BSelect

Cstring

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select instead of Zip will not combine sequences.

Using 'var' instead of 'string' in tuple element type causes errors.

Use Zip to combine sequences and specify tuple element types explicitly with 'string'.

5fill in blank

hard

Fill all three blanks to zip two arrays, filter pairs where sum is greater than 5, and create a list of sums.

C Sharp (C#)

int[] a = {1, 3, 5};
int[] b = {2, 4, 6};
var sums = a.[1](b, (x, y) => x + y)
            .Where(sum => sum [2] 5)
            .ToList();
Console.WriteLine(sums.[3]());

Drag options to blanks, or click blank then click option'

AZip

B>

CSum

DSelect

Attempts:

3 left

💡 Hint

Common Mistakes

Using Select instead of Zip for pairing.

Using '<' instead of '>' in the filter condition.

Using Count() instead of Sum() to get total.

Zip pairs elements, Where filters sums greater than 5, and Sum calculates total.

Practice

1.

What does the Zip method do in C#?

Choose the best description.

easy

A. Combines all elements from two collections into one long list.

B. Sorts elements in a collection in ascending order.

C. Filters elements from a collection based on a condition.

D. Pairs elements from two collections one by one until the shorter ends.

Solution

1. Step 1: Understand the purpose of Zip

   The Zip method pairs elements from two collections by their positions.

2. Step 2: Recognize stopping condition

   It stops when the shorter collection runs out of elements, so no extra elements are included.

3. Final Answer:

   Pairs elements from two collections one by one until the shorter ends. -> Option D

4. Quick Check:

   Zip pairs elements until the shorter ends = B [OK]

Hint: Zip pairs elements until shortest collection ends [OK]

Common Mistakes:

• Thinking Zip combines all elements regardless of length
• Confusing Zip with filtering or sorting
• Assuming Zip merges collections end-to-end

2.

Which of the following is the correct syntax to use Zip on two lists list1 and list2 to sum their elements?

var result = list1.Zip(list2, (a, b) => ? );

easy

A. a + b

B. a - b

C. a * b

D. a / b

Solution

1. Step 1: Identify the operation to sum elements

   The lambda expression should add the two elements: a + b.

2. Step 2: Confirm syntax correctness

   The syntax list1.Zip(list2, (a, b) => a + b) correctly sums paired elements.

3. Final Answer:

   a + b -> Option A

4. Quick Check:

   Sum elements with Zip = a + b [OK]

Hint: Use (a, b) => a + b to sum zipped elements [OK]

Common Mistakes:

• Using wrong operator like - or * instead of +
• Forgetting lambda syntax
• Mixing parameter order

3.

What is the output of this C# code?

var numbers = new[] {1, 2, 3};
var words = new[] {"one", "two"};
var zipped = numbers.Zip(words, (n, w) => $"{n}:{w}");
foreach(var item in zipped) Console.Write(item + " ");

medium

A. 1:one 2:two 3:

B. one:1 two:2

C. 1:one 2:two

D. 1:one 2:two 3:three

Solution

1. Step 1: Check lengths of arrays

   numbers has 3 elements, words has 2 elements; Zip stops at shorter length (2).

2. Step 2: Pair elements and format output

   Pairs: (1, "one"), (2, "two"); output strings: "1:one", "2:two".

3. Final Answer:

   1:one 2:two -> Option C

4. Quick Check:

   Zip stops at shorter list = C [OK]

Hint: Zip stops at shorter list length, so output matches shortest [OK]

Common Mistakes:

• Expecting output for all elements of longer list
• Mixing order of elements in output
• Adding extra spaces or elements

4.

Identify the error in this code snippet using Zip:

var a = new[] {1, 2, 3};
var b = new[] {4, 5};
var result = a.Zip(b, (x, y) => x + y).ToList();
Console.WriteLine(result[2]);

medium

A. Syntax error in Zip lambda expression

B. Index out of range exception at result[2]

C. Null reference exception

D. No error, prints 7

Solution

1. Step 1: Understand Zip output length

   Zip stops at shorter array length, so result has 2 elements only.

2. Step 2: Accessing invalid index

   Accessing result[2] (third element) causes IndexOutOfRangeException.

3. Final Answer:

   Index out of range exception at result[2] -> Option B

4. Quick Check:

   Accessing beyond Zip length causes error = A [OK]

Hint: Zip result length = shorter input length; check indexes [OK]

Common Mistakes:

• Assuming Zip output length equals longer list
• Ignoring zero-based indexing
• Confusing syntax errors with runtime errors

5.

You have two lists:

var keys = new[] {"a", "b", "c", "d"};
var values = new[] {1, 2, 3};

Using Zip, how can you create a dictionary that pairs keys and values only for matching positions?

hard

A. keys.Zip(values, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v)

B. keys.Select((k, i) => new {k, v = values[i]}).ToDictionary(x => x.k, x => x.v)

C. keys.Concat(values).ToDictionary(k => k, v => v)

D. values.Zip(keys, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v)

Solution

1. Step 1: Use Zip to pair keys and values

   Zip pairs elements by position, stopping at shorter list length (3 pairs).

2. Step 2: Convert pairs to dictionary

   Create anonymous objects with key and value, then call ToDictionary with key and value selectors.

3. Final Answer:

   keys.Zip(values, (k, v) => new {k, v}).ToDictionary(x => x.k, x => x.v) -> Option A

4. Quick Check:

   Zip pairs + ToDictionary = A [OK]

Hint: Zip keys and values, then ToDictionary with selectors [OK]

Common Mistakes:

• Using Concat instead of Zip
• Reversing keys and values in Zip
• Using Select without bounds check causing errors