Summary - Loops

Combine for, while and range-based for to write a multiplication table.

Summary - Loops

In this group you learned five loop tools: for, while, do-while, range-based for and break/continue. Each is designed for a different need.

Now you have two combined tasks. First you will print twice the numbers from 1 to 3 with for, then sum the numbers from 1 to 5 with while. Such accumulation and loop tasks appear all the time in real programs.

Exercise Print double (for)

Use a for (int i = 1; i <= 3; i++) loop to print twice the values 1, 2 and 3 with std::cout << (i * 2); on a single line. The output must be 246.

Show example solution

#include <iostream>

int main() {
    for (int i = 1; i <= 3; i++) {
        std::cout << (i * 2);
    }
    std::cout << std::endl;
    return 0;
}

Exercise Compute the sum (while)

The sum and i variables are set to 0 and 1. Inside a while (i <= 5) loop accumulate with sum += i; and increase i with i++. After the loop print sum with std::cout << sum;. The output must be 15.

Show example solution

#include <iostream>

int main() {
    int sum = 0;
    int i = 1;
    while (i <= 5) {
        sum += i;
        i++;
    }
    std::cout << sum << std::endl;
    return 0;
}

Test yourself

Which is a for loop that runs 5 times?
```
// counted loop
```
- for (int i = 0; i <= 5; i++)
- for (int i = 1; i < 5; i++)
- for (int i = 0; i < 4; i++)
- for (int i = 0; i < 5; i++)
Show answer

for (int i = 0; i < 5; i++) — i = 0, 1, 2, 3, 4 means 5 iterations.
Match each loop type to its scenario

for (int i = 0; i < n; i++)

Counted loop
while (cond)

While condition holds
do { } while (cond)

At least once
for (int x : v)

Over a collection

Write the range-based for symbol

std::vector<int> v = {1, 2, 3};
for (int x ____ v) { std::cout << x; }

Show answer

std::vector<int> v = {1, 2, 3};
for (int x : v) { std::cout << x; }

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