1051 Pop Sequence （PAT甲级）

1051. Pop Sequence (25)-PAT甲级真题（栈模拟）_柳婼的博客-CSDN博客

柳婼的解法比较直观一些。

我的解法如下：

#include 
#include 
#include 

int M, N, K, t;
bool flag;

int main(){
    scanf("%d %d %d", &M, &N, &K);
    for(int i = 0; i < K; ++i){
        std::vector vec(N);
        std::stack st;
        flag = true;
        t = 1;
        for(int j = 0; j < N; ++j){
            scanf("%d", &vec[j]);
            if(!flag){
                continue;
            }
            if(!st.empty() && st.top() > vec[j]){
                flag = false;
                continue;
            }
            if(!st.empty() && st.top() == vec[j]){
                st.pop();
            } else{
                if(t > vec[j]){
                    flag = false;
                    continue;
                }
                do{
                    st.push(t++);
                } while(st.top() < vec[j]);
                if(st.size() > M){
                    flag = false;
                    continue;
                }
                st.pop();
            }
        }
        printf("%s\n", flag ? "YES" : "NO");
    }
    return 0;
}

题目如下：

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