C#
Summary - Loops
Combine for, while and foreach to write a multiplication table.
Summary - Loops
In this group you learned for, while, do-while, foreach and break/continue. Now you will combine them to write a multiplication table.
Across two exercises you will first produce a 1-5 multiplication table with nested for, then sum a number array with foreach. Nested loops and accumulation meet here.
Exercise Write a multiplication table
Write two nested for loops: outer i from 1 to 3, inner j from 1 to 3. Each step prints i * j with Console.WriteLine. The output should be 1, 2, 3, 2, 4, 6, 3, 6, 9.
Show example solution
outer i (1-3), inner j (1-3). In the body write Console.WriteLine(i * j);
Example solution:
using System;
class Program
{
static void Main()
{
for (int i = 1; i <= 3; i++)
{
for (int j = 1; j <= 3; j++)
{
Console.WriteLine(i * j);
}
}
}
}
Exercise Sum an array with foreach
Declare a nums array: { 4, 8, 15 }. Set a sum variable to 0. Use foreach to add each element to sum (sum += n). After the loop, print sum with Console.WriteLine.
Show example solution
Write int[] nums = { 4, 8, 15 }; int sum = 0; foreach (var n in nums) { sum += n; } Console.WriteLine(sum);
Example solution:
using System;
class Program
{
static void Main()
{
int[] nums = { 4, 8, 15 };
int sum = 0;
foreach (var n in nums)
{
sum += n;
}
Console.WriteLine(sum);
}
}
The loops side by side
You now know five loop tools: for, while, do-while, foreach and break/continue. Which one to pick depends on the context.
When the count is known, for; condition first, while; at least once, do-while; walking a collection, foreach; early exit or skip, break/continue. Nested loops shine in multiplication tables and matrices.
Test yourself
-
Which loop runs the body at least once?
// which one?
Show answer
do-while — Correct. do-while checks the condition at the end; the body runs at least once.
-
Complete the nested for header
for (int i = 1; i <= 5; i++)
{
____ (int j = 1; j <= 5; j++)
{
Console.WriteLine(i * j);
}
}
Show answer
for (int i = 1; i <= 5; i++)
{
for (int j = 1; j <= 5; j++)
{
Console.WriteLine(i * j);
}
}
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