Prevent array from accepting duplicate values - c

Question

I have a stack where I want to push distinct elements. I wrote the following code. But it always checks only first element. If I enter a duplicate value first value, it doesn't accept that, but if I enter a duplicate value of 2nd or 3rd value it accepts it.
For example if I enter 20 and again enter 20 it will not accept the second,
but if I enter 20, 22, 22 it accepts the duplicate. How can I prevent this?
#include <stdio.h>
#define MAXSIZE 5
struct stack
{
int stk[MAXSIZE];
int top;
};
typedef struct stack STACK;
STACK s;
void push(void);
int pop(void);
void display(void);
void main ()
{
int choice;
int option = 1;
s.top = -1;
printf ("STACK OPERATION\n");
while (option)
{
printf ("------------------------------------------\n");
printf (" 1 --> Bus Status \n");
printf (" 2 --> Enter Bus \n");
printf (" 3 --> Exit Bus \n");
printf (" 4 --> EXIT \n");
printf ("------------------------------------------\n");
printf ("Enter your choice\n");
scanf ("%d", &choice);
switch (choice)
{
case 1:
display();
break;
case 2:
push();
break;
case 3:
pop();
break;
case 4:
return;
}
fflush (stdin);
printf ("Do you want to continue(Type 0 or 1)?\n");
scanf ("%d", &option);
}
}
/* Function to add an element to the stack */
void push ()
{
int num,i,j,status=0;
if (s.top == (MAXSIZE - 1))
{
printf ("Terminal is Full\n");
return;
}
else
{
printf ("Enter the Bus Number\n");
scanf ("%d", &num);
if(num<1 || num>30) {
printf("This bus Does not Exist.\n");
}
for(i=0;i<5;i++){
if(s.stk[i]==num){
printf("Bus Already in the Terminal\n");
break;
}
else {
s.top = s.top + 1;
s.stk[s.top] = num;
status=1;
break;
}
}
if(status==1)
printf("Bus %d Successfully Entered\n", num);
}
return;
}

Answer 1

You're bus insert loop is looping through and adds a bus the first time it finds s.stk[i] != num. You need to check to see if the bus is in the station ie search the whole stack before inserting a new bus.
for(i=0;i<5;i++) {
if(s.stk[i]==num){
printf("Bus Already in the Terminal\n");
break;
}
else {
s.top = s.top + 1;
s.stk[s.top] = num;
status=1;
break;
}
}