Find the Town Judge Problem & Solution
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.
See the find the town judge problem on LeetCode.
C++ Solution
#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")
#pragma GCC target("avx,avx2,fma")
static const int _=[](){std::ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();
class Solution {
public:
int findJudge(int n, vector<vector<int>>& trust) {
vector<int> incoming(n, 0);
vector<int> outgoing(n, 0);
for (int i = 0; i < trust.size(); ++i) {
++incoming[trust[i][1] - 1];
++outgoing[trust[i][0] - 1];
}
for (int i = 0; i < n; ++i) {
if (incoming[i] == n - 1 &&
outgoing[i] == 0) {
return i + 1;
}
}
return -1;
}
};