Question

我正在尝试创建一个菜单功能，循环回到现场0 a.k.a回到do while循环开始上方的菜单，当遇到第1点和第2点if语句时。任何人都可以提供一些帮助吗？

#include <stdio.h>          //library including standard input and output functions
#include <stdlib.h>         //library including exit and system functions used below
#include <string.h>         //library including string functions used


struct packet{
    int source;
    int destination;
    int type;
    int port;
    char data[50];
    char * filename;
};

int main ()
{
    struct packet s[50]; //Array for structure input
    char choice;
    int NetworkPacket = 0, ii = 0;
    int recordCount = 0;
///// SPOT 0//////
    do{

        system("cls");
        puts("Please enter an option:\n");
        puts("'A' Add a packet:\n");
        puts("'D' to Display the Packet List:\n");
        puts("'S' to Save the Packets to a file:\n");
        puts("'C' to Clear the list of current saved packets:\n");
        puts(" or X to exit the program...\n");

        //wait for user input
        scanf("%c", &choice);   //take the first char of user input and assing the value to
                                //the variable choice using the address of (&) the variable
        if(choice == '\n')      //check to see that the character is not \n left over from the
            scanf("%c", &choice);   //previous choice made, if it is then we need to scan the input again

        switch (choice)
        {
            case 'A': 
                system("cls"); //clear the screen
////SPOT 1//////
                if(NetworkPacket==50){
                    printf("No more network packets can be added");
                    getch();
                }
                else{}

 ////SPOT 1//////
                printf("\n****Adding a packet*****\n");
                printf("Where is the packet from?\n");
                scanf("%i", &s[NetworkPacket].source);
                printf("Where is the packet going?\n");
                scanf("%i", &s[NetworkPacket].destination);
                printf("What type is the packet?\n");
                scanf("%i", &s[NetworkPacket].type);
                printf("What is the packet's port?\n");
                scanf("%i", &s[NetworkPacket].port);
                printf("Enter up to 50 characters of data.\n");
                scanf("%s", s[NetworkPacket].data);
                NetworkPacket++;
                break;

            case 'D': 
                system("cls"); //clear the screen
                printf("\nDisplaying Infomation\n");
 ////SPOT 2//////
                if(NetworkPacket==0){
                    printf("no records yet, Please press any key to revert back to the main menu\n");
                    getch();
                }
                else{}
 ////SPOT 2//////
                for(ii = 0; ii < NetworkPacket; ii++) {    // adds a 1 onto the NetworkPacket counter keeping a tally on the number of records stored.
                    printf("\nSource: %d", s[ii].source);
                    printf("\nDestination: %d", s[ii].destination );
                    printf("\nType : %d", s[ii].type);
                    printf("\nPort : %dgetch();", s[ii].port);
                    printf("\nData: %s\n---\n", s[ii].data);
                } break;

            case 3: 
                break;

            system("cls");
            break;

            case 4: break;
            case 5: break;

            default:
                system("cls");
                printf("%c is not an option\n Try again...\n", choice);
        }
    }while(choice!='X' && (NetworkPacket >= 50? (printf("No more network packets can be added" ), 0) : 1));
    return 0;
}

Answer 1

像这样使用continue指令：

if (something_cool_happened)
    continue;

这将导致do-while循环结束当前迭代并返回循环的开头。这也适用于while循环和for循环

Answer 2

我不确定我是否正确理解了你的问题。但是要执行循环的下一次迭代，可以使用continue语句。

Answer 3

@ Dinesh的回答应该可以解决你的问题。但是，作为附加功能，当NetworkPacket＆gt; = 50时，您不希望允许用户显示或保存到文件吗？如果发生这种情况，你就会终止。您应该仅在用户尝试添加另一个NetworkPacket时检查此条件吗？

如果我误解了这个问题，请原谅我。

循环回菜单

3 个答案: