✅ Detailed Explanation of C Language Switch Statement Exercises

Yesterday, I assigned 3 mandatory exercises, and today we will analyze them in detail.

✅ By mastering this, you will firmly grasp the real application scenarios of switch!

📝 Exercise 1: Number to Day of the Week (1~7)

📌 Input: An integer (1-7) 📌 Output: Corresponding day of the week

✅ Analysis Approach

• 1~7 arefixed enumeration values → using switch is most suitable
• Use <span>default</span> to avoid out-of-bounds input

✅ Complete Code

#include <stdio.h>

int main() {
    int day;
    printf("请输入一个数字(1-7)：");
    scanf("%d", &day);

    switch(day) {
        case 1: printf("星期一\n"); break;
        case 2: printf("星期二\n"); break;
        case 3: printf("星期三\n"); break;
        case 4: printf("星期四\n"); break;
        case 5: printf("星期五\n"); break;
        case 6: printf("星期六\n"); break;
        case 7: printf("星期天\n"); break;
        default: printf("输入错误，请输入1-7！\n");
    }
    return 0;
}

✅ Example Execution

Input: 3
Output: 星期三

📌 Must-master technique: default is used to handle invalid input

📝 Exercise 2: Letter Grade A~F Output Evaluation

📌 Input: Character (A B C D E F) 📌 Output: Grade evaluation

✅ Analysis Approach

• Input may be lowercase → use case-insensitive writing
• First absorb the newline: <span>scanf(" %c", &grade);</span>

✅ Complete Code

#include <stdio.h>

int main() {
    char grade;
    printf("请输入成绩等级(A-F)：");
    scanf(" %c", &grade);  //前加空格避免回车干扰

    switch(grade) {
        case 'A':
        case 'a':
            printf("优秀！\n"); break;
        case 'B':
        case 'b':
            printf("良好！\n"); break;
        case 'C':
        case 'c':
            printf("中等！\n"); break;
        case 'D':
        case 'd':
            printf("及格！\n"); break;
        case 'E':
        case 'e':
        case 'F':
        case 'f':
            printf("不及格，需要努力！\n"); break;
        default:
            printf("输入无效！\n");
    }
    return 0;
}

✅ Example Execution

Input: b
Output: 良好！

📌 Technique: Merging case for uppercase and lowercase, structure isclear and elegant

📝 Exercise 3: Score Conversion to 5-Point Grading System

📌 Requirements

Score Range	Grade
90~100	A
80~89	B
70~79	C
60~69	D
<60	E

✅ Analysis Approach: The score isrange judgment → is if more suitable? No! We can use the range compression technique 👇

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score / 10 100/10 → 10 85/10 → 8 64/10 → 6

Thus, we can use switch for grouped judgment ✅

✅ Complete Code

#include <stdio.h>

int main() {
    int score, level;
    printf("请输入分数(0-100)：");
    scanf("%d", &score);

    if(score < 0 || score > 100){
        printf("输入错误！\n");
        return 0;
    }

    level = score / 10;

    switch(level){
        case 10:  //满分100归入A
        case 9: printf("等级：A\n"); break;
        case 8: printf("等级：B\n"); break;
        case 7: printf("等级：C\n"); break;
        case 6: printf("等级：D\n"); break;
        default: printf("等级：E\n"); break;
    }

    return 0;
}

✅ Example Execution

Input: 86
Output: 等级：B

📌 Technique: ✅ Range conversion to interval integers ✅ Multiple case merging ✅ Input validity check

✅ Summary

Through these three exercises, you have mastered:

Technique	Applied Exercise Number
Switch fixed option branches	✅ Exercise 1
Character judgment + reducing duplicate code	✅ Exercise 2
Range judgment compression technique	✅ Exercise 3
Default handling	✅ All
Input exception handling (robustness)	✅ Exercise 3

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🎯 Switch is one of the most important structures in menus, categories, and device control. Knowing how to use it + optimize it = you have surpassed ordinary beginners ✔️

📌 Next Lesson Preview

Coming soon 👇

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🔥 Detailed Explanation of C Language Loop Structures (for/while/do-while) + Multiplication Table + Summation + Console Effects