C语言if语句后如何跳转回代码顶部答案

【问题标题】：How to jump back to the top of the code after if statement C languageC语言if语句后如何跳转回代码顶部
【发布时间】：2020-05-29 07:45:29
【问题描述】：

在用户从菜单中选择一个选项后，我正试图让我的程序从头开始。当用户选择 1 然后输入捐赠金额时，我希望程序重新启动并显示菜单 What would you like to do? 而不仅仅是重新启动 if 语句。

我应该在 if 语句中添加一个 for 循环来完成这个吗？感谢您的帮助。

 printf("What would you like to do?\n");
    printf("      1 - Donate\n");
    printf("      2 - Invest\n");
    printf("      3 - Print balance\n");
    printf("      4 - Exit\n");
    printf("\n");

    //scans menu choice
    scanf("%d", &menu_option);

    if(menu_option==1)
    {
    printf("How much do you want to donate?\n");
    scanf("%lf", &donation);
    donations_made++;
    current_Balance = initial_Balance + donation;
    }

【问题讨论】：

将所有内容放入for(;;) { 并执行break; 以在除案例1 之外的所有情况下退出循环
把它放在一个循环中。

标签： c for-loop if-statement

【解决方案1】：

当用户选择1然后输入捐款金额时，我希望程序重新启动并显示菜单

只是做

for(;;) {
  printf("      1 - Donate\n");
  printf("      2 - Invest\n");
  printf("      3 - Print balance\n");
  printf("      4 - Exit\n");
  printf("\n");

  //scans menu choice
  scanf("%d", &menu_option);

  if(menu_option==1)
  {
    printf("How much do you want to donate?\n");
    scanf("%lf", &donation);
    donations_made++;
    current_Balance = initial_Balance + donation;
    // NO BREAK
  }
  else {
    .... management of other cases
    break;
  }
}

或者如果你喜欢

do {
  printf("      1 - Donate\n");
  printf("      2 - Invest\n");
  printf("      3 - Print balance\n");
  printf("      4 - Exit\n");
  printf("\n");

  //scans menu choice
  scanf("%d", &menu_option);

  if(menu_option==1)
  {
    printf("How much do you want to donate?\n");
    scanf("%lf", &donation);
    donations_made++;
    current_Balance = initial_Balance + donation;
  }
  // ... management of other cases
} while (menu_option==1);

但是您确定在情况 2 和 3 中也不想重做吗？在这种情况下，将while (menu_option==1); 替换为while (menu_option != 4); 或在第一个提案中，仅当menu_option 为4 时才使用break

我还鼓励您检查 scanf("%d", &menu_option); 的返回值，以确保在输入中给出了一个有效整数并设置了 menu_option

【讨论】：

【解决方案2】：

#include <stdio.h>

int main()

{
 int menu_option;
 double donation;
 int donations_made = 0;
 int current_Balance = 0;
 int initial_Balance = 0;

 for (;;)
 {

    printf("What would you like to do?\n");
    printf("      1 - Donate\n");
    printf("      2 - Invest\n");
    printf("      3 - Print balance\n");
    printf("      4 - Exit\n");
    printf("\n");

    //scans menu choice
    scanf("%d", &menu_option);

            if (menu_option==1)
            {
                   printf("How much do you want to donate?\n");
                   scanf("%lf", &donation);
                   donations_made++;
                   current_Balance = initial_Balance + donation;
             }
        else if (menu_option == 4)
                 break;

   }
}

【讨论】：