Learning C++ from Scratch: Practical Cases of if-else Conditional Statements
This article introduces the if-else conditional statement in C++, which is used to execute different operations based on conditions. The core idea is that if the condition is true, the corresponding code block is executed; otherwise, another block is executed, endowing the program with decision-making capabilities. There are three syntax forms: 1. Single condition: Use `if(condition)` to execute the corresponding code block. 2. Binary choice: Use `if-else`, where the if block runs if the condition is true, and the else block runs otherwise. 3. Multi-condition: Use `else if`, with conditions judged from top to bottom in descending order of scope (e.g., for grading, first check ≥90, then 80-89, etc.) to avoid logical errors. Practical cases include: - Determining odd/even numbers (using `%2 == 0`). - Grading scores (outputting A/B/C/D/F for 0-100, with handling for invalid scores). Key notes: - The condition expression must be a boolean value (e.g., use `==` instead of assignment `=`). - `else if` order must be from large to small ranges. - Braces are recommended for code blocks. - Avoid incorrect condition ranges. Summary: if-else is a fundamental control statement. Mastering its syntax and logical order allows handling more branches through nesting or switching, cultivating program decision-making thinking.
Read MoreA Comprehensive Guide to C++ if-else Conditional Statements: Fundamentals of Logical Judgment
The if-else conditional statement in C++ is fundamental to program control flow, enabling the execution of different branches based on conditions to achieve "either/or" or multi-condition judgment. Its core syntax includes: the basic structure `if(condition){...} else {...}` for handling two-branch logic; multi-branches extended with `else if`, where conditions are evaluated sequentially with short-circuit execution (subsequent conditions are not checked once a condition is met), as in determining grade levels from highest to lowest. Nested if-else can handle complex logic, such as checking for positive even numbers by nesting parity checks within the positive number branch. When using if-else, note that: conditions must be bool expressions (avoid non-explicit bool conditions like `num`); use `==` instead of `=` for comparison; else follows the "nearest principle"—it is recommended to always use braces to clearly define code block scopes; multi-condition judgments require reasonable ordering to avoid logical errors. Mastering these concepts allows flexible handling of branch logic and lays the foundation for advanced content like loops and functions.
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