课程进度 24% · 第5/18章第5/18章 · 标签 1/4
— 1 —
if 语句
cpp
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// 基本的 if 语句
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int age = 18;
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if (age >= 18) {
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cout << "您已成年" << endl;
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}
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// if-else 语句
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int score = 75;
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if (score >= 60) {
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cout << "及格" << endl;
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} else {
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cout << "不及格" << endl;
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}
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// if-else if-else 语句
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int grade = 85;
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if (grade >= 90) {
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cout << "优秀" << endl;
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} else if (grade >= 80) {
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cout << "良好" << endl;
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} else if (grade >= 60) {
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cout << "及格" << endl;
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} else {
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cout << "不及格" << endl;
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}
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// 嵌套的 if 语句
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bool hasID = true;
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if (age >= 18) {
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if (hasID) {
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cout << "可以办理" << endl;
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} else {
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cout << "请先办理身份证" << endl;
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}
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}
📖条件表达式必须是布尔类型或可转换为布尔类型。使用花括号可以提高代码可读性
— 2 —
switch 语句
cpp
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int day = 3;
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switch (day) {
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case 1: cout << "星期一" << endl; break;
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case 2: cout << "星期二" << endl; break;
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case 3: cout << "星期三" << endl; break;
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case 4: cout << "星期四" << endl; break;
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case 5: cout << "星期五" << endl; break;
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case 6:
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case 7: cout << "周末" << endl; break;
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default: cout << "无效日期" << endl;
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}
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// 不使用 break 的级联效果
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char grade = 'B';
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switch (grade) {
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case 'A': cout << "优秀" << endl; break;
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case 'B':
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case 'C': cout << "良好" << endl; break;
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case 'D': cout << "及格" << endl; break;
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default: cout << "不及格" << endl;
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}
📖switch 表达式必须是整数或枚举类型，case 标签必须是常量表达式，不要忘记 break