September 11Easy

Unique 3 digit even numbers

Array
Hash Table
Enumeration
Recursion

Problem

You are given an array of digits called digits. Your task is to determine the number of distinct three-digit even numbers that can be formed using these digits.

Note: Each copy of a digit can only be used once per number, and there may not be leading zeros.

Solution

class Solution:
    def totalNumbers(self, digits: List[int]) -> int:
        ans = 0
        n = len(digits)
        seen = set()
        for i in range(n):
            if digits[i] == 0:
                continue
            for j in range(n):
                if i == j:
                    continue
                for k in range(n):
                    if j == k or i == k or digits[k] % 2:
                        continue
                    if (digits[i], digits[j], digits[k]) not in seen:
                        ans += 1
                        seen.add((digits[i], digits[j], digits[k]))
        return ans