## DEV Community

Abhishek Chaudhary

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# 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:

1. The town judge trusts nobody.
2. Everybody (except for the town judge) trusts the town judge.
3. 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`

SOLUTION:

``````class Solution:
def findJudge(self, n: int, trust: List[List[int]]) -> int:
trustedGraph = {}
trustingGraph = {}
for a, b in trust:
trustedGraph[b] = trustedGraph.get(b, 0) + 1
trustingGraph[a] = trustingGraph.get(a, 0) + 1
for i in range(1, n + 1):
if trustedGraph.get(i, 0) == n - 1 and trustingGraph.get(i, 0) == 0:
return i
return -1
``````