## 1395. Count Number of Teams

There are `n` soldiers standing in a line. Each soldier is assigned a unique `rating` value.

You have to form a team of 3 soldiers amongst them under the following rules:

• Choose 3 soldiers with index (`i`, `j`, `k`) with rating (`rating[i]`, `rating[j]`, `rating[k]`).
• A team is valid if: (`rating[i] < rating[j] < rating[k]`) or (`rating[i] > rating[j] > rating[k]`) where (`0 <= i < j < k < n`).

Return the number of teams you can form given the conditions. (soldiers can be part of multiple teams).

Example 1:

```Input: rating = [2,5,3,4,1]
Output: 3
Explanation: We can form three teams given the conditions. (2,3,4), (5,4,1), (5,3,1).
```

Example 2:

```Input: rating = [2,1,3]
Output: 0
Explanation: We can't form any team given the conditions.
```

Example 3:

```Input: rating = [1,2,3,4]
Output: 4
```

Constraints:

• `n == rating.length`
• `3 <= n <= 1000`
• `1 <= rating[i] <= 105`
• All the integers in `rating` are unique.

## Rust Solution

``````struct Solution;

impl Solution {
fn num_teams(rating: Vec<i32>) -> i32 {
let n = rating.len();
let mut res = 0;
for i in 0..n {
for j in i + 1..n {
for k in j + 1..n {
if rating[i] < rating[j] && rating[j] < rating[k] {
res += 1;
}
if rating[i] > rating[j] && rating[j] > rating[k] {
res += 1;
}
}
}
}
res
}
}

#[test]
fn test() {
let rating = vec![2, 5, 3, 4, 1];
let res = 3;
assert_eq!(Solution::num_teams(rating), res);
let rating = vec![2, 1, 3];
let res = 0;
assert_eq!(Solution::num_teams(rating), res);
let rating = vec![1, 2, 3, 4];
let res = 4;
assert_eq!(Solution::num_teams(rating), res);
}
``````

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