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
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
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