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
分析：
該題的考點為棧的模擬控嗜。判斷一個序列是否為正確的出棧序列坑匠，即模擬棧的入棧出棧過程。
用一個隊列和一個棧來進(jìn)行運(yùn)算譬重。將待檢驗的序列放在隊列中棚菊，然后按照1-N的順序入棧罪塔。每入棧一次就判斷棧頂?shù)脑睾完犃蓄^部的元素是否相等若厚。如果相等就一直將隊列頭部和棧頂?shù)脑厝サ艋笸В钡讲幌嗟纫囊啊Ｈ缓蠼又霔０谜簦绱搜h(huán)。最后判斷棧是否為空：若棧為空悯搔，則序列合法骑丸，棧不為空，序列不合法。
#include <iostream>
#include <queue>
#include <stack>
using namespace std;
int main()
{
int M, N, K, num;
scanf_s("%d %d %d", &M, &N, &K);
/*while (K--)
{
}*/
for (int i = 0; i < K; i++)
{
stack<int> s;
queue<int> q;
for (int j = 0; j < N; j++)
{
scanf_s("%d", &num);
q.push(num);
}
for (int n = 1; n <= N; n++)
{
s.push(n);
if (s.size() > M)
{
break;
}
while (!s.empty() && s.top() == q.front())
{
s.pop();
q.pop();
}
}
if (s.empty())
{
printf("YES\n");
}
else
{
printf("NO\n");
}
}
system("pause");
return 0;
}
