Searching for Elements

In this lesson, you will learn to search for array elements using:

for
foreach
while
do...while

Searching using `for`

The for loop provides access to the index, which is convenient for searching.


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int[] numbers = { 4, 8, 15, 16, 23, 42 };
int target = 23; // value to find
bool found = false;
for (int i = 0; i < numbers.Length; i++)
{
    if (numbers[i] == target)
    {
        Console.WriteLine($"Found! Index: {i}");
        found = true;
        break;
    }
}
if (!found)
{
    Console.WriteLine("Element not found.");
Line 1, Char 1

Searching using `foreach`

foreach is simpler, but does not provide an index.


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int[] numbers = { 4, 8, 15, 16, 23, 42 };
int target = 23; // value to find
bool found = false;
foreach (int number in numbers)
{
    if (number == target)
    {
        Console.WriteLine("Element found!");
        found = true;
        break;
    }
}
if (!found)
{
    Console.WriteLine("Element not found.");
Line 1, Char 1

Searching using `while`

Suitable when the search logic is dynamic.


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int[] numbers = { 4, 8, 15, 16, 23, 42 };
int target = 23; // value to find
int i = 0;
bool found = false;
while (i < numbers.Length)
{
    if (numbers[i] == target)
    {
        Console.WriteLine($"Found! Index: {i}");
        found = true;
        break;
    }
    i++;
}
if (!found)
{
    Console.WriteLine("Element not found.");
Line 1, Char 1

Searching using `do...while`

The loop executes at least once.


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int[] numbers = { 4, 8, 15, 16, 23, 42 };
int target = 23; // value to find
int j = 0;
bool found = false;
do
{
    if (numbers[j] == target)
    {
        Console.WriteLine($"Found! Index: {j}");
        found = true;
        break;
    }
    j++;
}
while (j < numbers.Length);
if (!found)
{
    Console.WriteLine("Element not found.");
Line 1, Char 1

Summary

for — best option if you need to know the index.
foreach — when you just need to check for the presence of an element.
while — convenient for complex search conditions.
do...while — rarely used, but guarantees one iteration.

Exercises

Implement search using for.


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string[] names = { "Ivan", "Kate", "Pete", "Olga" };
string target = "Pete";
// Your code
Line 1, Char 1

Implement search using foreach.


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string[] names = { "Ivan", "Kate", "Pete", "Olga" };
string target = "Pete";
// Your code
Line 1, Char 1

Implement search using while.


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string[] names = { "Ivan", "Kate", "Pete", "Olga" };
string target = "Pete";
// Your code
Line 1, Char 1

Implement search using do…while.


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string[] names = { "Ivan", "Kate", "Pete", "Olga" };
string target = "Pete";
// Your code
Line 1, Char 1

Searching for Elements

Searching using for

Searching using foreach

Searching using while