Day 10 Find the Town Judge.cpp

PROBLEM:


In a town, there are N people labelled 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 trust, an array of pairs trust[i] = [a, b] representing that the person labelled a trusts the person labelled b.

If the town judge exists and can be identified, return the label of the town judge.  Otherwise, return -1.

 

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
Example 4:

Input: N = 3, trust = [[1,2],[2,3]]
Output: -1
Example 5:

Input: N = 4, trust = [[1,3],[1,4],[2,3],[2,4],[4,3]]
Output: 3



SOLUTION:

class Solution {
public:
    int findJudge(int N, vector<vector<int>>& trust) {
        
        unordered_map<int,int> m;
        int i,j,n,ans=-1,k;
        n=trust.size();
        
        for(i=0;i<n;i++)
        {
            m[trust[i][1]]++;
        }
        
        for(i=1;i<=N;i++)
        {
            if(m[i]==N-1 && ans==-1)
            {
                ans=i;
                break;
            }
            
        }
        
        if(ans!=-1)
        {
            for(i=0;i<n;i++)
            {
                if(trust[i][0]==ans)
                {
                    ans=-1;
                    break;
                }
            }
        }     
        
        return ans;
    }
};