---
title: 997. Find the Town Judge
tags: graph
description: share source code.
---

# 997. Find the Town Judge

class Solution {
    public int findJudge(int n, int[][] trust) {
        
        List<Integer>[] graph = new ArrayList[n + 1];
        Arrays.setAll(graph, v -> new ArrayList<>() );
        
        for(int t [] : trust){
            graph[ t[0]].add( t[1]);
        }
        int judge = -1;
        int cnt = 0;
        // 先找到 judge
        for(int i = 1; i <= n; i ++){
            if(graph[i].size() == 0){
                judge = i;
                // 超過ㄧ個以上的 judge
                if(++cnt > 1){
                    return -1;
                };
            }
        }
        //沒找到 judge
        if(judge == -1){
            return -1;
        }
        
         //有人不相信 judge => 可能不同獨立的 graph
        for(int i = 1; i <= n; i ++){
          if(judge == i){
              continue;
          }  

          if(!graph[i].contains(judge)){
              return -1;
          }
        }
            
            
        return judge;    
        
    }
    
    
}