PAT 1051. Pop Sequence (25)

http://pat.zju.edu.cn/contests/pat-a-practise/1051

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 51 2 3 4 5 6 73 2 1 7 5 6 47 6 5 4 3 2 15 6 4 3 7 2 11 7 6 5 4 3 2

Sample Output:

YESNONOYESNO

#include <stdio.h>#include <stack>using namespace std;int main(){int m, n, k;scanf("%d%d%d", &m, &n, &k);while (k--){stack<int> s;int cur = 1, tmp;bool flag = true;s.push(1);for (int i = 0; i < n; i++){scanf("%d", &tmp);if (tmp > cur){for (int j = cur + 1; j <= tmp; j++)s.push(j);if (s.size() > m) flag = false;cur = tmp;}else{if (s.top() != tmp)flag = false;}s.pop();}if (flag) printf("YES\n");else printf("NO\n");}return 0;}