数据结构基础之C语言Pop Sequence

7-1 Pop Sequence (10 分)

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

Solution

#include <stdio.h>
#include <stdlib.h>
int main()
{
    int stack[1000];
    int top,a,b,c,number;
    scanf("%d %d %d",&a,&b,&c);
    for(int i=1;i<=c;i++)
	{
        top=0;
        int flag=1,n=1;
        for(int j=1;j<=b;j++)
		{
            scanf("%d",&number);
            while((top==0||(stack[top]!=number))&&flag!=0)
			{
                stack[top+1]=n;
                top=top+1;
                if(top>a){
                    flag=0;
                    break;
                }
                n++;
            }
            if(top>=1&&stack[top]==number&&flag!=0)
                top=top-1;
        }
        if(flag!=0)
        printf("YES\n");
        else
        printf("NO\n");
 
    }
    return 0;
}