c++ - Switch case 程序在某个点不断循环。想不通

Question

我想我已经尽力了，但是当我按选项传递3时，它总是显示为选项3。案例1,2,3按预期工作，但4,5,6,7,8,9, 10 将自动像情况 3 一样出现。那么您认为缺少什么？

#include "stdafx.h"
#include <stdlib.h>
#include <iostream>
#include <sstream>
#include <stdio.h>
using namespace std;


int pgk, ch1, ch2; // variables for the Menu1 and Menu2
char ch3; // Variable for menu 3


int main()
{
        printf("1, Final Lab\n"); // first option
        printf("2, Exit\n");// second option
        cin >> ch1; // computer is going to scan the option from keyboard
        // Switch change the option depending of the number we put in the keyboard
        switch (ch1)
        {
        case 1:
        {
            goto Menu2; // if the user enters 1, it is going to send to send it to do the operations
        }
        case 2:
        {
            goto End; // if the user enters 2, it is going to end the program.
        }

    Menu2:
        printf(" --------------------------Menu-------------------\n");
        printf("1:Pounds to kilograms\n");
        printf("2:inches to centimeters\n"); 
        printf("3:cups to milliters\n"); 
        printf("4:seconds to minutes \n"); 
        printf("5:Knots to mph\n"); 
        printf("6:tip calculator\n"); 
        printf("7:Grade average\n"); 
        printf("8:target heart rate calculator\n");
        printf("9:discount calculator\n");
        printf("10:end\n"); 
        cin >> ch2; // enter the option the user wants
        switch (ch2) // Options
        {
        case 1: 
        {
            system("cls");
            int pkg;
            printf("Choose to convert pounds to kg or kg to pounds. Press 0 for 1st option and press any other number for 2nd option.\n");
            scanf_s("%f", &pkg);
            _asm
            {
                MOV EBX, pkg;
                CMP pkg, 0;
                JE pounds_kilos;
                JMP kilos_pounds;
            }

        pounds_kilos:
            float nguypounds, nguyconvert1, nguyanswer1;
            nguyconvert1 = 2.204622f;
            printf("Enter the amount of pounds you would like to convert to kilograms\n");
            scanf_s("%f", &nguypounds);

            _asm
            {

                FLD nguypounds;
                FDIV nguyconvert1;
                FST nguyanswer1;
            }
            printf("Your enter number of pounds to kilograms is %f\n", nguyanswer1);
            system("pause");
            goto Menu3;

        kilos_pounds:
            float nguykilos, nguyconvert2, nguyanswer2;
            nguyconvert2 = 2.204622f;
            printf("Enter the amount of kilograms you would like to convert to pounds\n");
            scanf_s("%f", &nguykilos);

            _asm
            {
                FLD nguykilos;
                FMUL nguyconvert2;
                FST nguyanswer2;
            }
            printf("Your enter number of kilograms to pounds is %f\n", nguyanswer2);
            goto Menu3;

        }

        case 2: // if the user enters 2
        {

            system("cls");
            int pkg;
            printf("Choose to convert inches to centimeters or centimeters to inches. Press 0 for 1st option and press any other number for 2nd option.\n");
            scanf_s("%f", &pkg);
            _asm
            {
                MOV EBX, pkg;
                CMP pkg, 0;
                JE inches_centimeters;
                JMP centimeters_inches;
            }

        inches_centimeters:
            float nguyinches, nguyconvert3, nguyanswer3;
            nguyconvert3 = 2.54f;
            printf("Enter the amount of inches you would like to convert to centimeters\n");
            scanf_s("%f", &nguyinches);

            _asm
            {

                FLD nguyinches;
                FMUL nguyconvert3;
                FST nguyanswer3;
            }
            printf("Your enter number of inches to centimeters is %f\n", nguyanswer3);
            goto Menu3;
        }
        centimeters_inches:
            float nguycentimeters, nguyconvert4, nguyanswer4;
            nguyconvert4 = 0.39370079f;
            printf("Enter the amount of centimeters you like to convert to inches\n");
            scanf_s("%f", &nguycentimeters);

            _asm
            {
                FLD nguycentimeters;
                FMUL nguyconvert4;
                FST nguyanswer4;
            }
            printf("Your enter number of centimeters to inches is %f\n", nguyanswer4);

            goto Menu3;

        }
        case 3: // if the user enter 3 
        {
            system("cls");
            int pkg;
            printf("Choose to convert cups to milliters or milliters to cups. Press 0 for 1st option and press any other number for 2nd option.\n");
            scanf_s("%f", &pkg);
            _asm
            {
                MOV EBX, pkg;
                CMP pkg, 0;
                JE cups_milliters;
                JMP milliters_cups;
            }

        cups_milliters:
            float nguycups, nguyconvert5, nguyanswer5;
            nguyconvert5 = 236.58823f;
            printf("Enter the amount of cups you would like to convert to milliters\n");
            scanf_s("%f", &nguycups);

            _asm
            {

                FLD nguycups;
                FMUL nguyconvert5;
                FST nguyanswer5;
            }
            printf("Your enter number of cups to milliters is %f\n", nguyanswer5);
            system("pause");

            goto Menu3;

        milliters_cups:
            float nguymilliters, nguyconvert6, nguyanswer6;
            nguyconvert6 = 236.58823f;
            printf("Enter the amount of milliters you like to convert to cups\n");
            scanf_s("%f", &nguymilliters);

            _asm
            {
                FLD nguymilliters;
                FDIV nguyconvert6;
                FST nguyanswer6;
            }
            printf("Your enter number of milliters to cups is %f\n", nguyanswer6);
            goto Menu3;

        }
        case 4: // if the user enters 4
        {
            system("cls");
            int pkg;
            printf("Choose to convert seconds to minutes or minutes to seconds. Press 0 for 1st option and press any other number for 2nd option.\n");
            scanf_s("%f", &pkg);
            _asm
            {
                MOV EBX, pkg;
                CMP pkg, 0;
                JE sec_min;
                JMP min_sec;
            }
        sec_min:
            float nguyseconds, nguyconvert7, nguyanswer7;
            nguyconvert7 = 60;
            printf("Enter the amount of seconds you would like to convert to minutes\n");
            scanf_s("%f", &nguyseconds);

            _asm
            {

                FLD nguyseconds;
                FDIV nguyconvert7;
                FST nguyanswer7;
            }
            printf("Your enter number of seconds to minutes is %f\n", nguyanswer7);
            goto Menu3;

        min_sec:
            float nguyminutes, nguyconvert8, nguyanswer8;
            nguyconvert8 = 60;
            printf("Enter the amount of minutes you like to convert to seconds\n");
            scanf_s("%f", &nguyminutes);

            _asm
            {
                FLD nguyminutes;
                FMUL nguyconvert8;
                FST nguyanswer8;
            }
            printf("Your enter number of minutes to seconds is %f\n", nguyanswer8);
            system("pause");
            goto Menu3;
        }
        case 5:
        {
            system("cls");
            int pkg;
            printf("Choose to knots to mph or mph to knots. P=ress 0 for 1st option and press any other number for 2nd option.\n");
            scanf_s("%f", &pkg);
            _asm
            {
                MOV EBX, pkg;
                CMP pkg, 0;
                JE knots_mph;
                JMP mph_knots;
            }
        knots_mph:
            float nguyknots, nguyconvert9, nguyanswer9;
            nguyconvert9 = 1.15f;
            printf("Enter the amount of knots you would like to convert to mph\n");
            scanf_s("%f", &nguyknots);

            _asm
            {

                FLD nguyknots;
                FMUL nguyconvert9;
                FST nguyanswer9;
            }
            printf("Your enter number of knots to mph is %f\n", nguyanswer9);
            goto Menu3;

        mph_knots:
            float nguymph, nguyconvert10, nguyanswer10;
            nguyconvert10 = 1.15f;
            printf("Enter the amount of mph you like to convert to knots\n");
            scanf_s("%f", &nguymph);

            _asm
            {
                FLD nguymph;
                FDIV nguyconvert10;
                FST nguyanswer10;
            }
            printf("Your enter number of minutes to seconds is %f\n", nguyanswer10);
            system("pause");
            goto Menu3;

        }
        case 6:
        {
            system("cls");
            float nguybill, nguytip, nguyamount;
            printf("Please enter the total amount of your bill\n");
            scanf_s("%f", &nguybill);
            printf("Now add the percentage you would like to tip. PLEASE ENTER IN PERCENTAGE IN DECIMAL FORM!\n");
            scanf_s("%f", &nguytip);

            _asm
            {
                fld nguybill
                    fld nguytip
                    fmul nguybill
                    fadd st(0), st(1)
                    fst nguyamount
            }
            printf("the the toal amount after tip is %f\n", nguyamount);
            goto Menu3;

        }
        case 7:
        {
            system("cls");
            float nguytest1, nguytest2, nguytest3, nguyave, nguytotave;
            nguyave = 3;
            printf("Please enter the grade of your first test.\n");
            scanf_s("%f", &nguytest1);
            printf("Please enter the grade of your second test.\n");
            scanf_s("%f", &nguytest2);
            printf("Please enter the grade of your thrid test.\n");
            scanf_s("%f", &nguytest3);
            _asm
            {
                fld nguytest1
                    fld nguytest2
                    fld nguytest3
                    fadd st(0), st(1)
                    fadd st(0), st(2)
                    fdiv nguyave
                    fst nguytotave
            }
            printf("Your average grade is %f", nguytotave);
            goto Menu3;
        }
        case 8:
        {
            system("cls");
            float nguyage, nguyageconst, nguymaxhr, nguytarghr, nguymulmax;
            nguyageconst = 220;
            nguymulmax = .70f;
            printf("Please enter the total amount of your age to find your max heart rate and target heart rate\n");
            scanf_s("%f", &nguyage);

            _asm
            {
                fld nguyage
                    fld nguyageconst
                    fsub nguyage
                    fst nguymaxhr
            }

            _asm
            {
                fld nguymaxhr
                    fmul nguymulmax
                    fst nguytarghr
            }
            printf("your max heart rate should be %f beat per minute\n", nguymaxhr);
            printf("and your target heart rate should be %f beats per minute\n", nguytarghr);
            goto Menu3;

        }
        case 9:
        {
            system("cls");
            float nguyogprice, nguydis, nguyoff, nguynamount;
            printf("Please enter the oringal price\n");
            scanf_s("%f", &nguyogprice);
            printf("Now enter the given discout. PLEASE ENTER IN PERCENTAGE IN DECIMAL FORM!\n");
            scanf_s("%f", &nguydis);

            _asm
            {
                fld nguyogprice
                    fld nguydis
                    fmul nguyogprice
                    fst nguyoff
            }

            _asm
            {
                fld nguyoff
                    fld nguyogprice
                    fsub st(0), st(1)
                    fst nguynamount
            }
            printf("The new sale price is %f\n", nguynamount);
            goto Menu3;

        }
        case 10: // if the user enters 5
        {
            goto End; //go to end
        }
        }

    Menu3: // This menu is going to ask if the user wants to continue the program
        printf(" -------------------------Question---------------------\n"); // display message 
        printf("Do you want to continue the program Y/N\n"); // display message
        cin >> ch3; // enter yes or no
        switch (ch3) // conditional 
        {
        case 'y': // if the user enters 'y'
        {
            goto Menu2; // go to menu 2 and continue the program 
        }
        case 'Y': // if the user enters 'Y'
        {
            goto Menu2; // go to menu 2 and continue the program
        }
        case 'n': // if the user enters 'n'
        {
            goto End; // finish the program
        }
        case 'N': // if the user enters 'N'
        {
            goto End; // finish the program
        }


        }

    End: // menu to end the program
        system("pause"); // pause the system
        return 0;// end program

    }   

Answer 1

在 case 3 之前的右大括号被错误地放置在那里，它关闭了 switch 语句。因此输入 3 到 9 都以情况 3 结束。

无意冒犯，但由于可维护性和效率较差(编译器的优化机会)，在非常特定的上下文之外使用 goto 长期以来一直被认为是极其糟糕的编程实践。投入时间和精力来理清代码和重组程序将会得到返回。