LeetCode 2729: Check if The Number is Fascinating Solution

Master LeetCode problem 2729 (Check if The Number is Fascinating), 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.

2729. Check if The Number is Fascinating

Easy

Hash Table Math

Problem Explanation

Explanation:

To solve this problem, we need to concatenate the number n with 2n and 3n, then check if the resulting concatenated number contains all digits from 1 to 9 exactly once and does not have any zeros.

Create a concatenated number by appending n, 2n, and 3n.
Check if the concatenated number contains all digits from 1 to 9 and no zeros.
Return true if the conditions are satisfied, false otherwise.

Time Complexity: O(1) Space Complexity: O(1)

Solution Code

class Solution {
    public boolean isFascinating(int n) {
        String concatenated = n + String.valueOf(2*n) + String.valueOf(3*n);
        if (concatenated.length() != 9) {
            return false;
        }
        
        int[] countDigits = new int[10];
        for (char c : concatenated.toCharArray()) {
            if (c == '0') {
                return false;
            }
            countDigits[c - '0']++;
        }
        
        for (int i = 1; i <= 9; i++) {
            if (countDigits[i] != 1) {
                return false;
            }
        }
        
        return true;
    }
}

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