變量不變c

Question

嗨，我是一個begginer c程序員，我試圖做一個過濾器應該改變一個變量取決於其他變量，但它似乎並沒有改變變量g1出於某種原因。我真的很喜歡我能得到的任何幫助，因爲我現在被困在這裏。謝謝

#include <stdio.h> 
#include <stdlib.h> 
#include <time.h> 


int main(void) 
{ 
    int car; 
    int g1; 
    int g2; 
    int sel1; 
    unsigned int iseed = (unsigned int)time(NULL);   
    srand (iseed); 
    g1 = 0; 
    car = rand() % 3 + 1; 
    printf("%d\n",car); 

    printf("select a door beetween 1 and 3\n "); 
    scanf ("%d",&sel1); 
    if (sel1 < 0) 
    { 
     printf("Invalid selection!\n"); 
     return 0; 
    } 
    if (sel1 > 3) 
    { 
     printf("Invalid selection!\n"); 
     return 0; 
    } 

    if (sel1 == 1) 
    { 
     if(car == 1) 
     { 
      g1 = 2; 
      g2 = 3; 
     } 
     if (car == 2); 
     { 
      g1 = 3; 
      g2 = 1; 
     } 
     if (car == 3); 
     { 
      g1 = 2; 
      g2 = 1; 
     } 
    } 

    if (sel1 == 2) 
    { 
     if(car == 1) 
     { 
      g1 = 3; 
      g2 = 2; 
     } 
     if (car == 2); 
     { 
      g1 = 1; 
      g2 = 3; 
     } 
     if (car == 3); 
     { 
      g1 = 1; 
      g2 = 2; 
     } 
    } 

     if (sel1 == 3) 
    { 
     if(car == 1) 
     { 
      g1 = 2; 
      g2 = 3; 
     } 
     if (car == 2); 
     { 
      g1 = 1; 
      g2 = 3; 
     } 
     if (car == 3); 
     { 
      g1 = 1; 
      g2 = 2; 
     } 
    } 

    printf("Behind door %d is a goat\n",g1); 



    return 0; 
} 

Appetintly我沒有足夠的細節，所以忽略這個即時通訊只是增加一些隨機的細節。在初等數學中，變量是表示數字的字母字符，稱爲變量的值，可以是任意的，不完全指定的或未知的。

Answer 1

我注意到你不指定的話sel1==0 你spesified它sel1>3和sel1==3和sel1==2和sel1==1和sel1<0應該發生什麼，但你不指定的話sel1==0我想，如果SEL1是G1不改0，但是改變，否則 可能像下面

scanf ("%d ",&sel1); 

輸入SEL1當條件後，你應該把一個空間並刪除;if(car==2)和if(car==3)

Answer 2

首先，如@BLUEPIXY建議，您應該刪除;。

我會改變前兩個SEL1條件僅有一個，比如這個：

if (sel1 < 1 || sel1 > 3) 
    printf("Invalid selection!\n"); 

然後我會用一個switch情況和if聲明：

#include <stdio.h> 
#include <stdlib.h> 
#include <time.h> 


int main(void) 
{ 
    int car; 
    int g1; 
    int g2; 
    int sel1; 
    unsigned int iseed = (unsigned int)time(NULL); 
    srand(iseed); 
    g1 = 0; 
    car = rand() % 3 + 1; 
    printf("Car= %d\n", car); 

    printf("Select a door beetween 1 and 3:\n"); 
    scanf("%d", &sel1); 


    if (sel1 < 1 || sel1 > 3) 
     printf("Invalid selection!\n"); 

    switch (sel1) 
    { 
    case 1: 
     if (car == 1) 
     { 
      g1 = 2; 
      g2 = 3; 
     } 
     else if (car == 2) 
     { 
      g1 = 3; 
      g2 = 1; 
     } 
     else if (car == 3) 
     { 
      g1 = 2; 
      g2 = 1; 
     } 

     break; 

    case 2: 
     if (car == 1) 
     { 
      g1 = 3; 
      g2 = 2; 
     } 
     else if (car == 2) 
     { 
      g1 = 1; 
      g2 = 3; 
     } 
     else if (car == 3) 
     { 
      g1 = 1; 
      g2 = 2; 
     } 
     break; 

    case 3: 
     if (car == 1) 
     { 
      g1 = 2; 
      g2 = 3; 
     } 
     else if (car == 2) 
     { 
      g1 = 1; 
      g2 = 3; 
     } 
     else if (car == 3) 
     { 
      g1 = 1; 
      g2 = 2; 
     } 
     break; 
    } 


    printf("Behind door, %d is a goat\n", g1); 


    getchar(); 
    getchar(); 

    return 0; 
} 

例子：