PAT-甲级-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 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

 1 #include <stdio.h>
 2 #include <stack>
 3 #include <stdbool.h>
 4 
 5 using namespace std;
 6 stack<int> st;
 7 
 8 const int maxn = 1010;
 9 int arr[maxn];
10 
11 int main()
12 {
13     int m, n, t;
14     scanf("%d%d%d",&m,&n,&t);
15     while(t--)
16     {
17         while( !st.empty() )
18         {
19             st.pop();
20         }
21 
22         for(int i = 1; i <= n; i++)
23         {
24             scanf("%d",&arr[i]);
25         }
26 
27         int cur = 1;
28         bool flag = true;
29         
30         for(int i =1; i <= n; i++)
31         {
32             st.push(i);      //把i压入栈
33             if(st.size() > m)  //控制栈的容量
34             {
35                 flag = false;
36                 break;
37             }
38 
39             while(!st.empty() && st.top() == arr[cur])
40             {
41                 st.pop();
42                 cur++;
43             }
44         }
45 
46         if(st.empty() == true && flag == true)
47         {
48             printf("YES\n");
49         }
50         else
51         {
52             printf("NO\n");
53         }
54     }
55     
56     return 0;
57 }