1051. Pop Sequence (25)

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.

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

YES
NO
NO
YES
NO

#include <iostream>
#include <vector>
using namespace std;
vector<int> inStack;
int mark[1010];
int main(void) {
	int n,m,k;
	cin >> m >> n >> k;
	for (int j = 0; j < k; j++) {
		int temp, maxPush = 0;
		
		bool flag = true;
		inStack.clear();
		for (int i = 0; i < 1002; i++) {
			mark[i] = 0;
		}
		cin >> temp;maxPush = temp;
		mark[temp]++;
		if (temp > m || temp < 0)
			flag = false;
		for (int i = 1; i < temp; i++) {
			inStack.push_back(i);
			mark[i] = 1;
		}
		for (int i = 1; i < n; i++) {
			int lastpop = temp;		
			cin >> temp;			
			mark[temp]++;
			if (temp > n || temp < 1)
				flag = false;
			
			if (temp <= maxPush + m - inStack.size() && temp>lastpop) {
				if (temp > maxPush)
					maxPush = temp;
				for (int q = lastpop + 1; q < temp; q++) {
					if(mark[q]==0)
						inStack.push_back(q);
					mark[q]++;
				}
			}
			
			else if (inStack.size()>0&&temp == inStack[inStack.size()-1]) {
				inStack.pop_back();
			}
			else {
				flag = false;
			}
		}
			
		if (flag == true)
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	return 0;
}