PAT 甲级 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.
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>
#include <vector>
#include <algorithm>
#include <cstring>
#include <stack>
using namespace std;

int main() {
int m, n, k;
scanf("%d %d %d", &m, &n, &k);
for (int i = 0; i < k; i++) {
bool flag = false;
stack<int>s;
vector<int> v(n + 1);
for (int j = 1; j <= n; j++) {
scanf("%d", &v[j]);
}
int current = 1;
for (int j = 1; j <= n; j++) {
s.push(j);
if (s.size() > m) break;
while (!s.empty() && s.top() == v[current]) {
s.pop();
current++;
}
}
if (current == n + 1) flag = true;
if (flag) printf("YES\n");
else printf("NO\n");
}
return 0;
}