Iteration in C++
Iteration in C++ refers to the process of repeating a set of instructions until a specific condition is met. This is typically achieved using loops. C++ provides several types of loops for iteration:
1. **`for` Loop**
The `for` loop is commonly used when the number of iterations is known in advance.
```cpp
for (initialization; condition; update) {
// Code to be executed
}
```
**Example:**
```cpp
#include <iostream>
using namespace std;
int main() {
for (int i = 0; i < 5; i++) {
cout << "Iteration: " << i << endl;
}
return 0;
}
```
**Output:**
```
Iteration: 0
Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
```
---
2. **`while` Loop**
The `while` loop is used when the number of iterations is not known in advance, and the loop continues as long as the condition is true.
```cpp
while (condition) {
// Code to be executed
}
```
**Example:**
```cpp
#include <iostream>
using namespace std;
int main() {
int i = 0;
while (i < 5) {
cout << "Iteration: " << i << endl;
i++;
}
return 0;
}
```
**Output:**
```
Iteration: 0
Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
```
---
3. **`do-while` Loop**
The `do-while` loop is similar to the `while` loop, but it guarantees that the loop body is executed at least once, even if the condition is false.
```cpp
do {
// Code to be executed
} while (condition);
```
**Example:**
```cpp
#include <iostream>
using namespace std;
int main() {
int i = 0;
do {
cout << "Iteration: " << i << endl;
i++;
} while (i < 5);
return 0;
}
```
**Output:**
```
Iteration: 0
Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4
```
---
4. **Range-based `for` Loop (C++11 and later)**
The range-based `for` loop is used to iterate over elements in a container (e.g., arrays, vectors, etc.).
```cpp
for (element : container) {
// Code to be executed
}
```
**Example:**
```cpp
#include <iostream>
#include <vector>
using namespace std;
int main() {
vector<int> numbers = {1, 2, 3, 4, 5};
for (int num : numbers) {
cout << "Number: " << num << endl;
}
return 0;
}
```
**Output:**
```
Number: 1
Number: 2
Number: 3
Number: 4
Number: 5
```
---
5. **Nested Loops**
Loops can be nested within each other to handle more complex iteration scenarios.
**Example:**
```cpp
#include <iostream>
using namespace std;
int main() {
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 2; j++) {
cout << "i = " << i << ", j = " << j << endl;
}
}
return 0;
}
```
**Output:**
```
i = 0, j = 0
i = 0, j = 1
i = 1, j = 0
i = 1, j = 1
i = 2, j = 0
i = 2, j = 1
```
---
6. **Control Statements in Loops**
- **`break`**: Exits the loop immediately.
- **`continue`**: Skips the rest of the loop body and proceeds to the next iteration.
- **`return`**: Exits the function (and thus the loop).
**Example:**
```cpp
#include <iostream>
using namespace std;
int main() {
for (int i = 0; i < 10; i++) {
if (i == 5) {
break; // Exit the loop when i is 5
}
if (i % 2 == 0) {
continue; // Skip even numbers
}
cout << "Odd Number: " << i << endl;
}
return 0;
}
```
**Output:**
```
Odd Number: 1
Odd Number: 3
```
---
Summary
- Use `for` loops when the number of iterations is known.
- Use `while` or `do-while` loops when the number of iterations is not known.
- Use range-based `for` loops for iterating over containers.
- Use `break`, `continue`, and `return` to control loop execution.
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