题目地址

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

作者: CHEN, Yue
单位: 浙江大学
时间限制: 400 ms
内存限制: 64 MB
代码长度限制: 16 KB

include<iostream>

#include<algorithm>
#include<math.h>
#include<vector>
#include<string>
#include<set>
#include<map>
#include<stack>
using namespace std;
typedef long long ll;
const int maxn=10010;

int main(){
    int m,n,k;
    cin>>m>>n>>k;
    while(k--){
        int flag=1,t,j=1;stack<int>st;
        for(int i=0;i<n;i++){
            cin>>t;
            if(!flag) continue;
            while(j<=t)st.push(j++);
            if(st.size()>m){
                flag=0;continue;
            }
            if(j==t) {
                st.pop();continue;
            }
            if(st.size())
            if(st.top()==t) st.pop();
            else if(st.top()>t) flag=0;
        }
        if(flag) cout<<"YES"<<endl;
        else cout<<"NO"<<endl;
    }
}