find-town-judge.js

/* Find the Town Judge

In a town, there are n people labeled from 1 to n.
There is a rumor that one of these people is secretly the town judge.

If the town judge exists, then:
    The town judge trusts nobody.
    Everybody (except for the town judge) trusts the town judge.
    There is exactly one person that satisfies properties 1 and 2.

You are given an array trust where trust[i] = [ai, bi] representing that the person labeled ai trusts the person labeled bi.

Return the label of the town judge if the town judge exists and can be identified, or return -1 otherwise.

Example 1:
Input: n = 2, trust = [[1,2]]
Output: 2

Example 2:
Input: n = 3, trust = [[1,3],[2,3]]
Output: 3

Example 3:
Input: n = 3, trust = [[1,3],[2,3],[3,1]]
Output: -1

Constraints:
    1 <= n <= 1000
    0 <= trust.length <= 104
    trust[i].length == 2
    All the pairs of trust are unique.
    ai != bi
    1 <= ai, bi <= n
*/

/**
 * @param {number} n
 * @param {number[][]} trust
 * @return {number}
 */
 var findJudge = function(n, trust) {
    let outDegree = new Array(n).fill(0);
    let inDegree = new Array(n).fill(0);
    let  res = -1;
    
    for(let i = 0; i < trust.length; i++){
        outDegree[trust[i][0] - 1]++;
        inDegree[trust[i][1] - 1]++;
    }
    
    for(let i = 0; i < n; i++){
       if(outDegree[i] === 0 && inDegree[i] === n - 1 ){
           res = i + 1;
           break;
       }
    }
    
    return res;
};