Pop Sequence

**题目描述
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.
输入描述:
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.
输出描述:
For each pop sequence, print in one line “YES” if it is indeed a possible pop sequence of the stack, or “NO” if not.
输入例子:
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
输出例子:
YES
NO
NO
YES
NO**

思路：模拟进出栈，关键是先想清楚再写。

#include<cstdio>
#include<stack>
using namespace std;
const int maxn=1005;
int a[maxn];
int M,K,N;
bool solve(){
    for(int i=0;i<K;i++){
        scanf("%d",&a[i]);
    }
    int cur=0,Size=0;
    stack<int>s;
    s.push(0);
    for(int i=0;i<K;i++){
        if(a[i]-cur+Size>M){
            return false;
        }
        else{
            if(a[i]>s.top()){
                for(int j=cur+1;j<=a[i];j++){
                        s.push(j);
                        Size++;
                    }
                cur=s.top();
                s.pop();
                Size--;
            }
            else if(a[i]==s.top()){
                s.pop();
                Size--;
            }
            else if(a[i]<s.top()){
                return false;
            }
        }
    }
    return true;
}
int main(){
    //freopen("in.txt","r",stdin);
    scanf("%d%d%d",&M,&K,&N);
    while(N--){
        if(solve()){
            puts("YES");
        }
        else{
            puts("NO");
        }
    }
    return 0;
}