스텍과 큐는 top, rear, front 변수의 초기값을 -1로 줘야 합니다.
씨언어에서의 배열은 첨자가 0부터 시작하기 때문에 반드시 모든 변수를 -1로 초기화 해줘야 결과값이 바르게 나옵니다.



>#include<stdio.h>                
>
>int top;                
>int stack[3];
>int Queue[3];
>int data;
>int head=0,tail=0;                        
>
>push()                        
>{
>        stack[++top] = data;        
>        return 0;
>}
>
>pop()                        
>{
>        stack[top--] = 0;                
>        return 0;
>}
>
>stackwrite()                
>{
>        int i;
>        printf("Stack : ");
>        for(i=top;i>0;i--)                        
>                printf("%3d",stack[i]);
>        return 0;
>}
>
>Q_push()                
>{
>        Queue[tail++] = data;                
>        return 0;
>}
>
>Q_pop()                        
>{
>        Queue[head++] = 0;                        
>        return 0;
>}
>
>Q_write()                        
>{
>        int i;
>        printf("\nQueue : ");                
>        for (i=head;i<tail;i++)                        
>                printf("%3d",Queue[i]);
>        return 0;
>}
>
>
>void main()                        
>{
>        int ch;
>        printf ("**************************************\n");
>        printf ("1. add                2. delete        3.exit\n");
>        printf ("**************************************\n");
>        for(;;)
>        {
>                printf("\n\nChoose : ");
>                scanf ("%d",&ch);
>                printf("\n");
>                if (ch==1)
>                {
>                        if (top > 2)
>                        {
>                                printf("overflow ...\n");
>                                break;
>                        }
>                        printf("Input : ");
>                        scanf("%3d",&data);
>                        push();
>                        Q_push();
>                        stackwrite();
>                        Q_write();
>                }
>                if (ch==2)
>                {
>                        if (top == 0)
>                        {
>                                printf("underflow ...\n");
>                                break;
>                        }
>                        pop();
>                        Q_pop();
>                        stackwrite();
>                        Q_write();
>                }
>                if (ch==3)
>                {
>                        break;
>                }                        
>                
>        }
>}
>
>
>