swap array

[lavender]

C programming

Below is my question and the code.

Write a program that will swap two values in an array. If the swap is successfull, the
program will display the updated list. If it contains any error, for example the values
are not in the list, the program will display appropriate error messages. Use related
functions to develop this program.
Example of outputs that the program must fulfill is as shown below (user input is in
bold font):

Example Output 1:
Key in value, 0 to stop: 6 8 11 35 64 0
list now : 6 8 11 35 64
value to change: 35
want to cahnge with: 8
list now: 6 35 11 8 64


Example Output 2:
Key in value, 0 to stop: 6 8 11 35 64 0
list now: 6 8 11 35 64
value to change: 35
want to cahnge with: 27
ERROR!! : no this number 27!
list now: 6 8 11 35 64

Example Output 3:
Key in value, 0 to stop: 0
list now: EMPTY LIST!



This is my code:

 #include <stdio.h> 
#define max 5
 
int main()
{
    int num[max], i=0;
    int swapFromNum = 0;
    int swapToNum = 0;
    int swapFromArrIndex = 0;
    int swapToArrIndex = 0;
    bool swapFromNumFound = false, swapToNumFound = false;
 
    printf("Enter value, 0 to stop: \n");
while(1)
{
scanf("%d", &num ); // read value
if(num[i]==0)
break; // if 0 finished
i++;
}
 
printf("List now: ");
 
     for(i=0;i<max;i++)
     {
        printf("%d ",num[i]);
     }
     printf("\n");
 
 
     printf("Value to change:");
     scanf("%d",&swapFromNum);
 
     for(i=0;i<max;i++)
     {
        if(num[i] == swapFromNum)
         {
            swapFromNumFound = true;
            swapFromArrIndex = i;
            }
        }
 
         if (swapFromNumFound == false)
     { 
         printf("ERROR!! : No this Value\n");
         } 
         return main();
 
 
 
     printf("Want change with value:");
     scanf("%d",&swapToNum);
 
 
        for(i=0;i<max;i++)
     {
        if(num[i] == swapToNum)
         {
            swapToNumFound = true;
            swapToArrIndex = i;
         }
     }
 
if(swapToNumFound == false)
     {
        printf("ERROR!! : No this value\n");
     }
 
 
    if(swapFromNumFound && swapToNumFound)
     {
         num[swapFromArrIndex] = swapToNum;
         num[swapToArrIndex] = swapFromNum;
         printf("List now: ");
         for(i=0;i<max;i++)
         {
         printf("%d ",num[i]);
     }
         printf("\n");
     }
 
}
 

my output is:

Enter value, 0 to stop:
1
2
0
List now: 1 2 0 4202500 37814140
value to change:


1. Why my output cannot stop after 0, it still auto generate the number which I didn't key in?

[horace1]

you enter 3 numbers into num[] but you print 5 elements hence the last two values are rubbish
you need to set max to the number of elements read, e.g.

#define MAX 5
 
int main()
{
    int num[MAX], i=0;
    int swapFromNum = 0;
    int swapToNum = 0;
    int swapFromArrIndex = 0;
    int swapToArrIndex = 0;
    bool swapFromNumFound = false, swapToNumFound = false;
 
    printf("Enter value, 0 to stop: \n");
while(1)
{
scanf("%d", &num[i] ); // read value
if(num[i]==0)
break; // if 0 finished
i++;
}
int max=i;   // note number of elements read
printf("List now: %d", max);
 
     for(i=0;i<max;i++)
     {
        printf("%d\n ",num[i]);
     }
     printf("\n");
 
 

[Ganon11]

In your while loop, you should also make sure the user cannot enter more than 5 numbers. Your array only has room for 5 elements, but your code will let them enter numbers in any position, possibly rewriting a lot of important data.