C/C++ 语言中的 if...else if...else 语句

1. if statement

The syntax of the if statement is:

if (condition) {
    // body of if statement
}

The code inside { } is the body of the if statement.

If the condition evaluates to true, the code inside the body of if is executed.

If the condition evaluates to false, the code inside the body of if is skipped.

2. if...else statement

If the boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed.

if(boolean_expression) {
    // statement(s) will execute if the boolean expression is true
} else {
    // statement(s) will execute if the boolean expression is false
}

If the condition evaluates true,

the code inside the body of if is executed
the code inside the body of else is skipped from execution

If the condition evaluates false,

the code inside the body of else is executed
the code inside the body of if is skipped from execution

3. if...else if...else statement

The syntax of the if...else if...else statement is:

if (condition1) {
    // code block 1
}
else if (condition2){
    // code block 2
}
else {
    // code block 3
}

If condition1 evaluates to true, the code block 1 is executed.

If condition1 evaluates to false, then condition2 is evaluated.

If condition2 is true, the code block 2 is executed.

If condition2 is false, the code block 3 is executed.

if (condition1) {
    // block of code to be executed if condition1 is true
} else if (condition2) {
    // block of code to be executed if the condition1 is false and condition2 is true
} else {
    // block of code to be executed if the condition1 is false and condition2 is false
}

References

[1] Yongqiang Cheng, https://yongqiang.blog.csdn.net/
[2] C++ if, if…else and Nested if…else, https://www.programiz.com/cpp-programming/if-else