Detailed explanation and examples of C++ loops

In C++ programming, loops (Loops) are an important control structure used to execute the same or similar multiple timesCode block, thereby achieving repetitive tasks and operations. This article will introduce several common types in C++Circular structure, their usage and examples help you fully understand the application and implementation of loops.

1. while loop

whileThe loop checks whether the condition is true before each iteration, and if it is true, the statement inside the loop body is executed.

#include <iostream>

int main() {
    int count = 1;
    
    while (count <= 5) {
        std::cout << "Count: " << count << std::endl;
        count++;
    }
    
    return 0;
}

Analysis:

Circulation conditions: count <= 5, check before each iterationcountWhether it is less than or equal to 5.
Circulation body: implementstd::coutOutput the currentcountvalue, thencountSelf-increasing.

2. do-while loop

do-whileThe loop executes the loop body first, then checks whether the condition is true, and if it is true, continues the loop.

#include <iostream>

int main() {
    int count = 1;
    
    do {
        std::cout << "Count: " << count << std::endl;
        count++;
    } while (count <= 5);
    
    return 0;
}

Analysis:

Circulation body: Execute firststd::coutOutput the currentcountvalue, thencountSelf-increasing.
Circulation conditions: count <= 5, check after each iterationcountWhether it is less than or equal to 5, and if so, continue to execute.

3. for loop

forLoops provide a concise way to iterate over the code, which contains initialization statements, loop conditions, and iterative expressions.

#include <iostream>

int main() {
    for (int count = 1; count <= 5; count++) {
        std::cout << "Count: " << count << std::endl;
    }
    
    return 0;
}

Analysis:

Initialization statement: int count = 1, initialize before entering the loopcountvariable.
Circulation conditions: count <= 5, check before each iterationcountWhether it is less than or equal to 5.
Die Representative Proposition: count++, after each cycle is overcountvalue.

4. Nested Loop

In C++, one or more loops can be nested inside a loop to achieve more complex control flows and logic.

#include <iostream>

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

Analysis:

External loopfor (int i = 1; i <= 3; i++)Control variablesiThe value of 1 to 3.
Internal loopfor (int j = 1; j <= 3; j++)Control variablesjThe value of 1 to 3 is performed once in each iteration of the outer loop.

5. Loop control statement

In a loop, control statements can also be used to control the execution flow of the loop, e.g.break、continueandgoto。

Example:

break: Terminate loop execution in advance.

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        break;  // Loop out when i equals 3
    }
    std::cout << "i: " << i << std::endl;
}

continue: Skip the current iteration and continue to execute the next iteration.

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        continue;  // Skip this iteration when i equals 3
    }
    std::cout << "i: " << i << std::endl;
}

goto: Jump to the label position in the program.

int i = 1;
loop:   // Label
if (i <= 5) {
    std::cout << "i: " << i << std::endl;
    i++;
    goto loop;  // Jump to the tag loop to continue execution
}

6. Choice of loop

When choosing which loop structure to use, it is usually determined based on specific requirements and code logic:

usewhileLoop when you need to execute a certain piece of code repeatedly according to the conditions.
useforLooping when you need a concise loop control structure, especially when the number of iterations is known.
usedo-whileLoop when you need to execute the loop body at least once, and then execute it repeatedly according to the conditions.
Use nested loops to process multidimensional data or require complex iterative logic to be executed.

Conclusion

Through the introduction of this article, you should have mastered several common loop structures and their application scenarios in C++. Loops are an important tool in programming that can help us handle repetitive tasks and data efficiently. In practical applications, selecting the appropriate loop structure according to specific needs and flexibly applying it in combination with control statements can improve the clarity of the code and execution efficiency. Hope this article can be helpful to your loop application in C++ programming.