Pop Sequence

Posted 2020-12-13 waiting-nobody

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

#include<iostream>
using namespace std;
struct stack
{
    int* array;
    int size;
    int top;
};
void creat_stack(stack*& x, int n)
{
    x->array = new int[n];
    memset(x->array, 0, sizeof(int) * n);
    x->size = n;
    x->top = -1;
}
bool Is_empty(stack*& x)
{
    return (x->top == -1);
}
bool Is_full(stack*& x)
{
    return (x->top == x->size - 1);
}
bool push(stack*& x, int a)
{
    if (Is_full(x))
    {
        cout << "The stack is full.
";
        return 0;
    }
    else
    {
        x->array[++x->top] = a;
        return 1;
    }
}
int pop(stack*& x)
{
    if (Is_empty(x))
    {
        cout << "The stack is empty.
";
        exit(0);
    }
    else
    {
        return x->array[x->top--];
    }
}
bool judge_it(int* x, int m, int n)
{
    stack* s = new stack;
    creat_stack(s, m);
    int flag = 1; bool judge = 1;
    for (int i = 0; i < n; i++)
    {
        if (Is_empty(s))
        {
            while (flag <= x[i])
            {
                if (Is_full(s))
                    return false; 
                else
                    push(s, flag++);
            }
            pop(s);
        }
        else
        {
            int temp = pop(s);
            if (x[i] > temp)
            {
                push(s, temp);
                while (flag <= x[i])
                {
                    if (Is_full(s))
                        return false;
                    else
                        push(s, flag++);
                }
                pop(s);
            }
            if (x[i] < temp)
                return false;
        }
    }
    return true;
}
int main()
{
    int m = 0, n = 0, k = 0;
    cin >> m >> n >> k;
    int* array = new int[n];
    bool* judge = new bool[k];
    for (int i = 0; i < k; i++)
    {        
        for (int j = 0; j < n; j++)
            cin >> array[j];
        judge[i] = judge_it(array, m, n);
    }
    for (int i = 0; i < k; i++)
    {
        if (judge[i])
            cout << "Yes
";
        else 
            cout << "No
";
    }
}