Use switch statements to select different situations

switch and case are commonly used structures in programming, used to execute different code blocks based on different conditions. This article will introduce the usage of switch and case in detail and provide specific code examples.

The switch statement is a multi-branch selection structure that accepts an expression as a parameter and selects the corresponding code block for execution based on the value of the expression. The switch statement is usually used in conjunction with the case statement, which is used to define specific branches and corresponding execution codes. When the value of the expression is equal to the value of a case, the code block under the case will be executed.

The syntax structure of the switch statement is as follows:

switch(表达式) {
  case 值1:
    // 执行代码块1
    break;
  case 值2:
    // 执行代码块2
    break;
  ...
  default:
    // 执行默认代码块
    break;
}

In the above code, the expression is a variable or expression, which is used to determine which case code block is specifically executed. Each case is followed by a colon (:), indicating the code block under that case. The break statement is used to jump out of the switch statement to avoid continuing to execute other cases. The default keyword is used to specify the default code block to be executed when no case is matched.

The following is a practical example showing how to use switch and case:

#include <iostream>
using namespace std;

int main() {
  int num = 2;
  switch(num) {
    case 1:
      cout << "数字是1" << endl;
      break;
    case 2:
      cout << "数字是2" << endl;
      break;
    case 3:
      cout << "数字是3" << endl;
      break;
    default:
      cout << "数字不是1、2、3" << endl;
      break;
  }
  return 0;
}

In the above code, we define an integer variable num and assign it a value of 2. According to the value of num, the switch statement will execute the code block under the corresponding case. Since the value of num is 2, the code block under the second case will be executed and "the number is 2" will be output.

In addition to integer variables, the switch statement can also be used to determine other types of variables, such as character types, enumeration types, etc.

It should be noted that each case in the switch statement must be followed by a break statement to terminate the case, otherwise the code of the next case will continue to be executed. If the code block of a certain case does not need to be terminated, it can be replaced with an empty statement or using a special comment.

The above is an introduction to the usage of switch and case and specific code examples. By using switches and cases flexibly, we can write clearer and more readable code. I hope this article can be helpful to your study!

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