在菜单中创建菜单

Question

我正在尝试在菜单中制作菜单。我的问题是“ choice”的值未更改，因此当我尝试更改选择值时，程序停止运行，例如当我首先输入（2）时，然后输入（0），而当输入（1）时，程序将终止。

#include <stdio.h>

int choice, choiceJR;

void mainMenu() {
  printf("Select one of the following. \n");  
  printf("1. x \n");
  printf("2. menuJR \n");
  printf("3. xxx \n");

  printf("Choice: \n");
  scanf("%d", &choice);
}

void menuJR() {
  printf("Select one of the following. \n");
  printf("1. y \n");
  printf("2. yy \n");
  printf("0. go back \n");

  printf("Choice: \n");
  scanf("%d", &choiceJR);

}

int main() {

  mainMenu();

  while(choice != 1 && choice!= 2 && choice!= 3) {
    printf("Invalid choice! \n");
    mainMenu();
  }
  if(choice == 1) {
    printf("You have selected 1 \n");
  }
  else if(choice == 2) {
    printf("You have selected 2 \n");
    menuJR();
    while(choiceJR != 0) {
      menuJR();
    }
    if(choiceJR == 0) {
      printf("Going to menu! \n");
      mainMenu();
    }
  }
  else if(choice == 3) {
    printf("You have selected 3 \n");
  }


  return 0;
}

Answer 1

• 您应该使用do_while循环来选择项目。

• 这是您的解决方案，请使用此代码。

  #include <stdio.h>
  
  int choiceJR=0;
  
  int mainMenu() {
      int choice=0;
      printf("Select one of the following. \n");  
      printf("1. x \n");
      printf("2. menuJR \n");
      printf("3. xxx \n");
  
      printf("Choice: \n");
      scanf("%d", &choice);
      return choice;
  }
  
  void menuJR() {
      printf("Select one of the following. \n");
      printf("1. y \n");
      printf("2. yy \n");
      printf("0. go back \n");
  
      scanf("%d", &choiceJR);
  }
  
  int main() {
      int ch=0;
  
      do {
          main:
          ch = mainMenu();
          while(ch != 1 && ch!= 2 && ch!= 3) {
              printf("Invalid choice! \n");
              mainMenu(ch);
          }
  
          switch(ch) {
              case 1:
                  printf("You have selected 1 \n");
                  break;
  
              case 2:
                  printf("You have selected 2 \n");
                  menuJR();
                  while(choiceJR != 0) {
                      menuJR();
                  }
                  if(choiceJR == 0) {
                      printf("Going to menu! \n");
                      goto main;
                  }
                  break;
  
              case 3:
                  printf("You have selected 3 \n");
                  break;
  
              default: 
                  printf("invalid choice \n");
          }
  
      }
      while(ch<=3);
  
      return 0;
  }