AtCoder Beginner Contest 175
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Problem Statement
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We have sticks numbered $1, \cdots, N$. The length of Stick $i$ $(1 \leq i \leq N)$ is $L_i$.
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In how many ways can we choose three of the sticks with different lengths that can form a triangle?
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That is, find the number of triples of integers $(i, j, k)$ $(1 \leq i < j < k \leq N)$ that satisfy both of the following conditions:
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$L_i$,$L_j$, and$L_k$are all different.- There exists a triangle whose sides have lengths
$L_i$,$L_j$, and$L_k$.
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Constraints
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$1 \leq N \leq 100$$1 \leq L_i \leq 10^9$- All values in input are integers.
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Input
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Input is given from Standard Input in the following format:
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N
L_1 L_2 \cdots L_N翻译中…
Output
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Print the number of ways to choose three of the sticks with different lengths that can form a triangle.
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样例
Input #1
5
4 4 9 7 5
Output #1
5
The following five triples $(i, j, k)$ satisfy the conditions: $(1, 3, 4)$, $(1, 4, 5)$, $(2, 3, 4)$, $(2, 4, 5)$, and $(3, 4, 5)$.
Input #2
6
4 5 4 3 3 5
Output #2
8
We have two sticks for each of the lengths $3$, $4$, and $5$. To satisfy the first condition, we have to choose one from each length.
There is a triangle whose sides have lengths $3$, $4$, and $5$, so we have $2 ^ 3 = 8$ triples $(i, j, k)$ that satisfy the conditions.
Input #3
10
9 4 6 1 9 6 10 6 6 8
Output #3
39
Input #4
2
1 1
Output #4
0
No triple $(i, j, k)$ satisfies $1 \leq i < j < k \leq N$, so we should print $0$.
题目信息
题面与样例版权归 AtCoder 及出题人所有；中文翻译由 AI 生成（CI 管线），如有出入请以原文为准。