LeetCode 997: Find the Town Judge Solution

Master LeetCode problem 997 (Find the Town Judge), 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.

997. Find the Town Judge

Easy

Array Hash Table Graph

Problem Explanation

Explanation:

To solve this problem, we can create two arrays: trustCount and isTrusted. The trustCount array will store the count of people trusting each person, and the isTrusted array will store whether a person trusts someone or not.

We will iterate through the trust array and update these arrays. After that, we will check for the person who is trusted by all others (trustCount[i] == n-1) and doesn't trust anyone (isTrusted[i] == false). This person will be considered as the town judge. If there is no such person, we return -1.

Time complexity: O(N), where N is the number of people in the town.
Space complexity: O(N) for the two arrays.

Solution Code

class Solution {
    public int findJudge(int n, int[][] trust) {
        int[] trustCount = new int[n+1];
        boolean[] isTrusted = new boolean[n+1];
        
        for (int[] t : trust) {
            int a = t[0];
            int b = t[1];
            trustCount[b]++;
            isTrusted[a] = true;
        }
        
        for (int i = 1; i <= n; i++) {
            if (trustCount[i] == n-1 && !isTrusted[i]) {
                return i;
            }
        }
        
        return -1;
    }
}

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