LeetCode 2094: Finding 3-Digit Even Numbers Solution

Master LeetCode problem 2094 (Finding 3-Digit Even Numbers), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2094. Finding 3-Digit Even Numbers

Easy

Array Hash Table Sorting Enumeration

Problem Explanation

Explanation

To solve this problem, we can generate all possible 3-digit numbers by permuting the given digits and check if each number is even. We can use a recursive approach to generate all permutations. For each permutation, we check if the number is even and has 3 digits. If it meets these conditions, we add it to our result set.

Algorithm:
1. Generate all permutations of 3 digits from the input array.
2. For each permutation, check if it forms a 3-digit even number without leading zeros.
3. Add the valid numbers to a set to ensure uniqueness.
4. Return the sorted list of unique even numbers.
Time Complexity: The time complexity of this approach is O(n!) where n is the number of digits in the input array. Generating all permutations of the digits will take factorial time complexity.
Space Complexity: The space complexity is O(n) to store the set of valid 3-digit even numbers.

Solution Code

import java.util.*;

class Solution {
    public List<Integer> findNumbers(int[] digits) {
        Set<Integer> result = new HashSet<>();
        boolean[] visited = new boolean[digits.length];
        
        generatePermutations(digits, new ArrayList<>(), visited, result);
        
        List<Integer> resultList = new ArrayList<>(result);
        Collections.sort(resultList);
        return resultList;
    }
    
    private void generatePermutations(int[] digits, List<Integer> currNum, boolean[] visited, Set<Integer> result) {
        if (currNum.size() == 3) {
            int num = currNum.get(0) * 100 + currNum.get(1) * 10 + currNum.get(2);
            if (num % 2 == 0) {
                result.add(num);
            }
            return;
        }
        
        for (int i = 0; i < digits.length; i++) {
            if (!visited[i]) {
                visited[i] = true;
                currNum.add(digits[i]);
                generatePermutations(digits, currNum, visited, result);
                currNum.remove(currNum.size() - 1);
                visited[i] = false;
            }
        }
    }
}

Try It Yourself

Loading code editor...

Frequently Asked Questions

How to solve LeetCode 2094 (Finding 3-Digit Even Numbers)?

This page provides optimized solutions for LeetCode problem 2094 (Finding 3-Digit Even Numbers) in Java, C++, and Python, along with a detailed explanation and an interactive code editor to test your code.

What is the time complexity of LeetCode 2094 (Finding 3-Digit Even Numbers)?

The time complexity for LeetCode 2094 (Finding 3-Digit Even Numbers) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

Can I run code for LeetCode 2094 on DevExCode?

Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 2094 in Java, C++, or Python.

Back to LeetCode Solutions