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 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

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#include<iostream>#include<stack>using namespace std;int m,n,k;int a[1005];int main(){    cin>>m>>n>>k;    for (int i=0;i<k;i++)    {        for (int j=0;j<n;j++)        {            cin>>a[j];        }        int index1=0;        stack<int> s;        for (int j=1;j<=n;j++)        {            s.push(j);            if (s.size()>m)                break;            while(s.size()&&s.top()==a[index1])            {                s.pop();                index1++;            }        }        if (s.size()!=0)            cout<<"NO"<<endl;        else            cout<<"YES"<<endl;    }    return 0;}