浙大PAT出棧序列：7-3 Pop Sequence

Given a stack which can keep M numbers at most. Push N numbers in the order of 1, 2, 3, …, N and pop randomly. You are supposed to tell if a given sequence of numbers is a possible pop sequence of the stack. For example, if M is 5 and N is 7, we can obtain 1, 2, 3, 4, 5, 6, 7 from the stack, but not 3, 2, 1, 7, 5, 6, 4.

Input Specification:
Each input file contains one test case. For each case, the first line contains 3 numbers (all no more than 1000): M (the maximum capacity of the stack), N (the length of push sequence), and K (the number of pop sequences to be checked). Then K lines follow, each contains a pop sequence of N numbers. All the numbers in a line are separated by a space.

Output Specification:
For each pop sequence, print in one line “YES” if it is indeed a possible pop sequence of the stack, or “NO” if not.

Sample Input:

5 7 5
1 2 3 4 5 6 7
3 2 1 7 5 6 4
7 6 5 4 3 2 1
5 6 4 3 7 2 1
1 7 6 5 4 3 2

Sample Output:

YES
NO
NO
YES
NO

思路很簡單：將不大於當前出棧的元素全部入棧，再模擬出棧過程，若某刻棧頂元素比出棧元素要大，證明該出棧元素錯誤出棧。（ps）棧滿後入棧報錯

#include <stdio.h>
#include <malloc.h>
#include <stdbool.h>
#define ERROR -1
#define MaxNum 1005
typedef int ElementType;
typedef int Position;
struct SNode {
    ElementType *Data; /* 存儲元素的數組 */
    Position Top;      /* 棧頂指針 */
    int MaxSize;       /* 堆棧最大容量 */
};
typedef struct SNode *Stack;
 
Stack CreateStack( int MaxSize )
{
    Stack S = (Stack)malloc(sizeof(struct SNode));
    S->Data = (ElementType *)malloc(MaxSize * sizeof(ElementType));
    S->Top = -1;
    S->MaxSize = MaxSize;
    return S;
}
 
bool IsFull( Stack S )
{
    return (S->Top == S->MaxSize-1);
}
 
bool Push( Stack S, ElementType X )
{
    if ( IsFull(S) ) {
        //printf("堆棧滿");
        return false;
    }
    else {
        S->Data[++(S->Top)] = X;
        return true;
    }
}
 
bool IsEmpty( Stack S )
{
    return (S->Top == -1);
}
 
ElementType Pop( Stack S )
{
    if ( IsEmpty(S) ) {
        //printf("堆棧空");
        return ERROR; /* ERROR是ElementType的特殊值，標誌錯誤 */
    }
    else 
        return ( S->Data[(S->Top)--] );
}

ElementType Top(Stack S){
	if(IsEmpty(S)){
		//printf("堆棧空");
		return ERROR;
	}
	else
		return S->Data[S->Top];
}

int isPopSequence(int* pushSeq,int* popSeq,Stack S,int SeqLen){
	int push_i=0,pop_i=0;
	
	S->Top=-1;
	while(pop_i<SeqLen){
		if(Top(S)<popSeq[pop_i]){
			while(Top(S)<popSeq[pop_i]){
//				if(!Push(S,pushSeq[push_i++]))	return 0;
				if(IsFull(S)) return 0;
				Push(S,pushSeq[push_i++]);
			}
		}
		else if(Top(S)==popSeq[pop_i]){
			Pop(S);
			pop_i++;
		}
		else{
			return 0;
		}
	}
	if(pop_i==SeqLen)
		return 1;
}

int main()
{
	freopen("1.txt","r",stdin);
	int M,N,K;
	int pushSeq[MaxNum];
	int popSeq[MaxNum]={0};
	scanf("%d %d %d",&M,&N,&K);
	for(int a=0;a<N;a++)
		pushSeq[a] = a+1; 
	Stack S=CreateStack(K);
	for(;K>0;K--){
		for(int i=0;i<N;i++){
			scanf("%d",&popSeq[i]);
		}
		if(isPopSequence(pushSeq,popSeq,S,N)==1)
			printf("YES\n");
		else
			printf("NO\n");
	}
	return 0;
}