Count Number of Teams — LeetCode 1395 Python Solution

The problem

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

Example

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).

Python solution

class Solution:
    def numTeams(self, rating: List[int]) -> int:
        ans, n = 0, len(rating)
        for i, b in enumerate(rating):
            l = sum(a < b for a in rating[:i])
            r = sum(c > b for c in rating[i + 1 :])
            ans += l * r
            ans += (i - l) * (n - i - 1 - r)
        return ans

Complexity

Pattern: Dynamic Programming

Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 1395. Count Number of Teams is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Dynamic Programming.

The dynamic programming guide has the Python template for the pattern and the 481 LeetCode problems that use it.

Related problems