题目描述
Problem Description
Bob is facing a row of $n$ black stones, numbered from $1$ to $n$. The $i$-th stone has an integer $a_i$ written on it, and the integers on the $n$ stones form a permutation. The adjacent stones of the $i$-th stone are the $(i-1)$-th and $(i+1)$-th stones, if they exist.
Bob performs $n$ operations as follows:
- In the first step, he chooses any $i$ ($1 \le i \le n$) and paints the $i$-th stone white.
- From the second to the $n$-th step, he selects the black stone $j$ with the smallest $a_i$ among those whose adjacent stones include at least one white stone, and paints it white.
It is clear that after all steps are completed, all $n$ stones will be white.
Alice has chosen $q$ pairs of values $p_j$ and $k_j$. For each pair of $p$ and $k$, she wants to know how many different ways there are to choose which stone to paint white in the first step, such that the $p$-th stone becomes white in the $k$-th step.
Help Bob answer Alice's $q$ queries.
Input Format
The first line contains two integers $n$ and $q$, representing the number of stones and the number of queries, respectively.
The second line contains $n$ integers $a_1, a_2, \dots, a_n$, representing the integers written on the stones.
The next $q$ lines each contain a pair of integers $p_j$ and $k_j$.
Output Format
For each query, output a single integer representing the answer to the query.
Sample Input and Output
Sample Input #1
6 4
1 4 6 5 2 3
3 1
2 2
6 3
4 3
Sample Output #1
1
2
1
2
Sample Input #2
5 3
5 2 3 4 1
2 3
4 4
3 2
Sample Output #2
0
1
1
Notes/Hints
The bold numbers in the sample explanations indicate the stones that are painted white.
In the first sample:
- If the first step chooses the 1st stone:
- Step 1: $[\bold1, \gray4, \gray6, \gray5, \gray2, \gray3]$;
- Step 2: $[\bold1, \bold4, \gray6, \gray5, \gray2, \gray3]$;
- Step 3: $[\bold1, \bold4, \bold6, \gray5, \gray2, \gray3]$;
- Step 4: $[\bold1, \bold4, \bold6, \bold5, \gray2, \gray3]$;
- Step 5: $[\bold1, \bold4, \bold6, \bold5, \bold2, \gray3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
- If the first step chooses the 2nd stone:
- Step 1: $[\gray1, \bold4, \gray6, \gray5, \gray2, \gray3]$;
- Step 2: $[\bold1, \bold4, \gray6, \gray5, \gray2, \gray3]$;
- Step 3: $[\bold1, \bold4, \bold6, \gray5, \gray2, \gray3]$;
- Step 4: $[\bold1, \bold4, \bold6, \bold5, \gray2, \gray3]$;
- Step 5: $[\bold1, \bold4, \bold6, \bold5, \bold2, \gray3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
- If the first step chooses the 3rd stone:
- Step 1: $[\gray1, \gray4, \bold6, \gray5, \gray2, \gray3]$;
- Step 2: $[\gray1, \bold4, \bold6, \gray5, \gray2, \gray3]$;
- Step 3: $[\bold1, \bold4, \bold6, \gray5, \gray2, \gray3]$;
- Step 4: $[\bold1, \bold4, \bold6, \bold5, \gray2, \gray3]$;
- Step 5: $[\bold1, \bold4, \bold6, \bold5, \bold2, \gray3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
- If the first step chooses the 4th stone:
- Step 1: $[\gray1, \gray4, \gray6, \bold5, \gray2, \gray3]$;
- Step 2: $[\gray1, \gray4, \gray6, \bold5, \bold2, \gray3]$;
- Step 3: $[\gray1, \gray4, \gray6, \bold5, \bold2, \bold3]$;
- Step 4: $[\gray1, \gray4, \bold6, \bold5, \bold2, \bold3]$;
- Step 5: $[\gray1, \bold4, \bold6, \bold5, \bold2, \bold3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
- If the first step chooses the 5th stone:
- Step 1: $[\gray1, \gray4, \gray6, \gray5, \bold2, \gray3]$;
- Step 2: $[\gray1, \gray4, \gray6, \gray5, \bold2, \bold3]$;
- Step 3: $[\gray1, \gray4, \gray6, \bold5, \bold2, \bold3]$;
- Step 4: $[\gray1, \gray4, \bold6, \bold5, \bold2, \bold3]$;
- Step 5: $[\gray1, \bold4, \bold6, \bold5, \bold2, \bold3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
- If the first step chooses the 6th stone:
- Step 1: $[\gray1, \gray4, \gray6, \gray5, \gray2, \bold3]$;
- Step 2: $[\gray1, \gray4, \gray6, \gray5, \bold2, \bold3]$;
- Step 3: $[\gray1, \gray4, \gray6, \bold5, \bold2, \bold3]$;
- Step 4: $[\gray1, \gray4, \bold6, \bold5, \bold2, \bold3]$;
- Step 5: $[\gray1, \bold4, \bold6, \bold5, \bold2, \bold3]$;
- Step 6: $[\bold1, \bold4, \bold6, \bold5, \bold2, \bold3]$.
This problem uses bundled test cases.
| Subtask Number | Points | Special Conditions |
|---|---|---|
| 1 | 20 | $n, q \le 300$ |
| 2 | 17 | $n \le 3000$ |
| 3 | 12 | $n \le 50000, q \le 10$ |
| 4 | 6 | $a_i$ values are increasing |
| 5 | 16 | All $k_i$ are equal |
| 6 | 15 | All $p_i$ are equal |
| 7 | 14 | No special conditions |
For 100% of the data, $2 \le n \le 10^5$, $1 \le q \le 10^5$, $1 \le a_i \le n$ with all $a_i$ distinct, and $1 \le p_j, k_j \le n$.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分