A10064 | Geometric Progression
时间限制1s
内存限制256MB
通过 / 提交0/0
题目描述
Polycarp loves geometric progressions very much. Since he was only three years old, he loves only the progressions of length three. He also has a favorite integer $k$ and a sequence $a$ , consisting of $n$ integers.
He wants to know how many subsequences of length three can be selected from $a$ , so that they form a geometric progression with common ratio $k$ .
A subsequence of length three is a combination of three such indexes $i_{1},i_{2},i_{3}$ , that $1<=i_{1}<i_{2}<i_{3}<=n$ . That is, a subsequence of length three are such groups of three elements that are not necessarily consecutive in the sequence, but their indexes are strictly increasing.
A geometric progression with common ratio $k$ is a sequence of numbers of the form $b·k^{0},b·k^{1},...,b·k^{r-1}$ .
Polycarp is only three years old, so he can not calculate this number himself. Help him to do it.
He wants to know how many subsequences of length three can be selected from $a$ , so that they form a geometric progression with common ratio $k$ .
A subsequence of length three is a combination of three such indexes $i_{1},i_{2},i_{3}$ , that $1<=i_{1}<i_{2}<i_{3}<=n$ . That is, a subsequence of length three are such groups of three elements that are not necessarily consecutive in the sequence, but their indexes are strictly increasing.
A geometric progression with common ratio $k$ is a sequence of numbers of the form $b·k^{0},b·k^{1},...,b·k^{r-1}$ .
Polycarp is only three years old, so he can not calculate this number himself. Help him to do it.
输入格式
The first line of the input contains two integers, $n$ and $k$ ( $1<=n,k<=2·10^{5}$ ), showing how many numbers Polycarp's sequence has and his favorite number.
The second line contains $n$ integers $a_{1},a_{2},...,a_{n}$ ( $-10^{9}<=a_{i}<=10^{9}$ ) — elements of the sequence.
The second line contains $n$ integers $a_{1},a_{2},...,a_{n}$ ( $-10^{9}<=a_{i}<=10^{9}$ ) — elements of the sequence.
输出格式
Output a single number — the number of ways to choose a subsequence of length three, such that it forms a geometric progression with a common ratio $k$ .
输入输出样例
输入 #1
5 2 1 1 2 2 4
输出 #1
4
输入 #2
3 1 1 1 1
输出 #2
1
输入 #3
10 3 1 2 6 2 3 6 9 18 3 9
输出 #3
6
In the first sample test the answer is four, as any of the two 1s can be chosen as the first element, the second element can be any of the 2s, and the third element of the subsequence must be equal to 4.
C++ 编辑器
输入
输出
可保存默认模板;新题优先使用已保存模板。
当前快捷键仅展示,暂不支持修改。
- 撤销
Ctrl / ⌘ + Z - 重做
Ctrl / ⌘ + Y - 查找
Ctrl / ⌘ + F - 全选
Ctrl / ⌘ + A - 复制
Ctrl / ⌘ + C - 剪切
Ctrl / ⌘ + X - 粘贴
Ctrl / ⌘ + V - 自动排版
工具栏排版按钮 - 草稿保存
编辑时自动保存到本机
历史
提交记录
状态说明时间源码
AI
作答助手
你好,我是作答助手。可以问思路、复杂度、样例含义或代码报错原因;不会直接给出完整 AC 代码。
确定要清空代码吗?
提交通过
评测结果:Accepted