能否将C语言数字转英文程序中的if(tens!=1)改为switch语句？

问题描述 #

原本计划用if-else编写接收1-9999整数并转换为对应英文单词的程序，现已改为使用switch语句实现，当前代码运行正常，但希望将代码中的if (tens != 1)语句替换为switch语句，寻求可行方案。

当前代码如下：

#include<stdio.h>
#include<conio.h>

main()
{
  int num,thousands,hundreds,tens,ones;
  printf("Enter number (1-9999): ");
  scanf("%d",&num);
  if (num < 1 || num > 9999)
     printf("Invalid number.");
  else
  {
  thousands = num / 1000;
  hundreds = num % 1000 / 100;
  tens = num % 1000 % 100 / 10;
  ones = num % 1000 % 100 % 10;
  
    switch(thousands) {
    case 1: printf("one thousand"); break;
    case 2: printf("two thousand"); break;
    case 3: printf("three thousand"); break;
    case 4: printf("four thousand"); break;
    case 5: printf("five thousand"); break;
    case 6: printf("six thousand"); break;
    case 7: printf("seven thousand"); break;
    case 8: printf("eight thousand"); break;
    case 9: printf("nine thousand"); break;
    }

    switch(hundreds) {
    case 0: break;
    case 1: printf(" one hundred"); break;
    case 2: printf(" two hundred"); break;
    case 3: printf(" three hundred"); break;
    case 4: printf(" four hundred"); break;
    case 5: printf(" five hundred"); break;
    case 6: printf(" six hundred"); break;
    case 7: printf(" seven hundred"); break;
    case 8: printf(" eight hundred"); break;
    case 9: printf(" nine hundred"); break;
    }

    switch(tens) {
    {
    case 1: 
    {
        switch(ones) {
            case 0: printf(" ten");break;
            case 1: printf(" eleven"); break;
            case 2: printf(" twelve"); break;
            case 3: printf(" thirteen"); break;
            case 4: printf(" fourteen"); break;
            case 5: printf(" fifteen"); break;
            case 6: printf(" sixteen"); break;
            case 7: printf(" seventeen"); break;
            case 8: printf(" eighteen"); break;
            case 9: printf(" nineteen"); break;
        }
        break;
    }
    break;
    }
        
    case 2: printf(" twenty"); break;
    case 3: printf(" thirty"); break;
    case 4: printf(" forty"); break;
    case 5: printf(" fifty"); break;
    case 6: printf(" sixty"); break;
    case 7: printf(" seventy"); break;
    case 8: printf(" eighty"); break;
    case 9: printf(" ninety"); break;

    }

    if (tens != 1)
    {   
        switch(ones) {
            case 0: break;
            case 1: printf(" one"); break;
            case 2: printf(" two"); break;
            case 3: printf(" three"); break;
            case 4: printf(" four"); break;
            case 5: printf(" five"); break;
            case 6: printf(" six"); break;
            case 7: printf(" seven"); break;
            case 8: printf(" eight"); break;
            case 9: printf(" nine"); break;
        }

    }

}
getch();
}

解决方案 #

完全可以将if (tens != 1)替换为switch语句，利用switch匹配tens的所有可能取值（0-9），仅在tens不为1的分支中处理个位数字的输出，tens=1时直接跳过即可。

替换后的代码片段如下：

// 替换原有的if (tens != 1)块
switch(tens) {
    case 1:
        // 十位为1时已处理过10-19的英文，此处无需处理个位
        break;
    case 0:
    case 2:
    case 3:
    case 4:
    case 5:
    case 6:
    case 7:
    case 8:
    case 9:
        switch(ones) {
            case 0: break;
            case 1: printf(" one"); break;
            case 2: printf(" two"); break;
            case 3: printf(" three"); break;
            case 4: printf(" four"); break;
            case 5: printf(" five"); break;
            case 6: printf(" six"); break;
            case 7: printf(" seven"); break;
            case 8: printf(" eight"); break;
            case 9: printf(" nine"); break;
        }
        break;
}

额外优化建议 #

1. 原代码中tens的switch块存在多余的嵌套大括号，可删除以简化代码结构；
2. C标准中main函数应声明为int main()并返回0，符合规范；
3. <conio.h>是DOS时代的头文件，在现代编译器中可能不被支持，可考虑移除getch()，改用return 0;结束程序。

内容的提问来源于stack exchange，提问作者yourfriendlyneighborhoodcat