Algorithm
Problem Name: 997. 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. If a trust relationship does not exist in trust array, then such a trust relationship does not exist.
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 <= 10000 <= trust.length <= 104trust[i].length == 2- All the pairs of
trustare unique. ai != bi1 <= ai, bi <= n
Code Examples
#1 Code Example with Java Programming
Code -
Java Programming
class Solution {
public int findJudge(int n, int[][] trust) {
int[] trustScore = new int[n + 1];
for (int[] trustPair : trust) {
trustScore[trustPair[1]]++;
trustScore[trustPair[0]]--;
}
for (int i = 1; i < = n; i++) {
if (trustScore[i] == n - 1) {
return i;
}
}
return -1;
}
}
Input
Output
#2 Code Example with Javascript Programming
Code -
Javascript Programming
const findJudge = function(N, trust) {
const arr = new Array(N + 1).fill(0)
for(let [t, ted] of trust) {
arr[t]--
arr[ted]++
}
for(let i = 1; i < = N; i++) {
if(arr[i] === N - 1) return i
}
return -1
};
Input
Output
#3 Code Example with Python Programming
Code -
Python Programming
class Solution:
def findJudge(self, N: int, trust: List[List[int]]) -> int:
j, cnt = collections.Counter(b for a, b in trust).most_common(1)[0] if trust else (N, 0)
return j if j not in {a for a, b in trust} and cnt == N - 1 else -1
Input
Output
#4 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _0997_FindTheTownJudge
{
public int FindJudge(int N, int[][] trust)
{
var score = new int[N + 1];
foreach (var pair in trust)
{
score[pair[0]]--;
score[pair[1]]++;
}
for (int i = 1; i < N + 1; i++)
{
if (score[i] == N - 1)
return i;
}
return -1;
}
}
}
Input
Output