6-18 Two Stacks In One Array（20 point(s)）

6-18 Two Stacks In One Array（20 point(s)）

Write routines to implement two stacks using only one array. Your stack routines should not declare an overflow unless every slot in the array is used.

Format of functions:

Stack CreateStack( int MaxElements );
int IsEmpty( Stack S, int Stacknum );
int IsFull( Stack S );
int Push( ElementType X, Stack S, int Stacknum );
ElementType Top_Pop( Stack S, int Stacknum );

where int Stacknum is the index of a stack which is either 1 or 2;int MaxElements is the size of the stack array; and Stack is defined as the following:

typedef struct StackRecord *Stack;
struct StackRecord  {
    int Capacity;       /* maximum size of the stack array */
    int Top1;           /* top pointer for Stack 1 */
    int Top2;           /* top pointer for Stack 2 */
    ElementType *Array; /* space for the two stacks */
}

Note: Push is supposed to return 1 if the operation can be done successfully, or 0 if fails. If the stack is empty,Top_Pop must return ERROR which is defined by the judge program.

Sample program of judge:

#include <stdio.h>
#include <stdlib.h>
#define ERROR 1e8
typedef int ElementType;
typedef enum { push, pop, end } Operation;

typedef struct StackRecord *Stack;
struct StackRecord  {
    int Capacity;       /* maximum size of the stack array */
    int Top1;           /* top pointer for Stack 1 */
    int Top2;           /* top pointer for Stack 2 */
    ElementType *Array; /* space for the two stacks */
};

Stack CreateStack( int MaxElements );
int IsEmpty( Stack S, int Stacknum );
int IsFull( Stack S );
int Push( ElementType X, Stack S, int Stacknum );
ElementType Top_Pop( Stack S, int Stacknum );

Operation GetOp();  /* details omitted */
void PrintStack( Stack S, int Stacknum ); /* details omitted */

int main()
{
    int N, Sn, X;
    Stack S;
    int done = 0;

    scanf("%d", &N);
    S = CreateStack(N);
    while ( !done ) {
        switch( GetOp() ) {
        case push: 
            scanf("%d %d", &Sn, &X);
            if (!Push(X, S, Sn)) printf("Stack %d is Full!\n", Sn);
            break;
        case pop:
            scanf("%d", &Sn);
            X = Top_Pop(S, Sn);
            if ( X==ERROR ) printf("Stack %d is Empty!\n", Sn);
            break;
        case end:
            PrintStack(S, 1);
            PrintStack(S, 2);
            done = 1;
            break;
        }
    }
    return 0;
}

/* Your function will be put here */

Sample Input:

5
Push 1 1
Pop 2
Push 2 11
Push 1 2
Push 2 12
Pop 1
Push 2 13
Push 2 14
Push 1 3
Pop 2
End

Sample Output:

Stack 2 is Empty!
Stack 1 is Full!
Pop from Stack 1: 1
Pop from Stack 2: 13 12 11

code：
Stack CreateStack( int MaxElements ){
	Stack s = (Stack)malloc(sizeof(struct StackRecord));//申请一个栈的结构体空间 
	s->Array = (ElementType)malloc(MaxElements);//申请数组的大小空间 
	s->Top1 = -1;//栈1从头开始 
	s->Top2 = MaxElements;//栈2从尾开始 
	s->Capacity = MaxElements;//容量为数组大小 
	return s;//返回 
}
int IsEmpty( Stack S, int Stacknum ){
	if(Stacknum==1){//栈1 
		if(S->Top1==-1)return 1;//如果top1是-1为空 
		else return 0;
	}
	else{//栈2 
		if(S->Top2==S->Capacity)return 1;//如果top2是最大值为空 
		else return 0;
	}
}
int IsFull( Stack S ){
	if(S->Top1+1==S->Top2)return 1;//如果两个顶相邻，则满
	else return 0; 
} 
int Push( ElementType X, Stack S, int Stacknum ){
	if(Stacknum==1){//push栈1 
		if(IsFull(S))return 0;//如果满了返回0 
		else{//否则push进去 
			S->Array[++S->Top1] = X;
			return 1;
		}
	}
	else{//push栈2 
		if(IsFull(S))return 0;//栈满返回0 
		else{//否则push 
			S->Array[--S->Top2] = X;
			return 1;
		}
	}
}
ElementType Top_Pop( Stack S, int Stacknum ){
	if(Stacknum==1){
		if(IsEmpty(S,1))return ERROR;//为空返回error 
		else {
			int t = S->Array[S->Top1];//否则返回栈顶值 
			S->Top1--;//弹出 
			return t;
		}
	}
	else{
		if(IsEmpty(S,2))return ERROR;
		else {
			int t = S->Array[S->Top2];//同理 
			S->Top2++;;
			return t;
		}
	}
}