Node.js) BOJ 20040번 : 사이클게임

https://www.acmicpc.net/problem/20040

 

const fs=require('fs');
const filepath=process.platform==='linux'?'dev/stdin':'./input.txt';
const input = fs.readFileSync(filepath).toString().trim().split("\n");

input[0]=input[0].split(" ").map(n=>+n);
const node=input[0][0];
const times=input[0][1];

class Edge{
  constructor(from, to){
    this.from=from;
    this.to=to;
  }
}

class UnionFind{
  constructor(n){
    this.parent=new Array(n);;// Js에서는 그냥 this.parent=[]; 로만 해도 아래 인덱스 다 적용됨.
    this.size=new Array(n).fill(0);
    for(let i=0;i<n;++i){
      this.parent[i]=i;
    }
  }

  find(x){
    if(x==this.parent[x])return x;
    return this.parent[x]=this.find(this.parent[x]);
  }
  union(x1, x2){
    if(this.size[x1]<this.size[x2]){
      this.size[x2]+=this.size[x1];
      this.size[x1]=0;
      this.parent[x1]=x2;
    }
    else{
      this.size[x1]+=this.size[x2];
      this.size[x2]=0;
      this.parent[x2]=x1;
    }
  }
}

let edges=[];
for(let i=1;i<=times;++i){
  input[i]=input[i].split(" ").map(num=>+num);
  edges.push(new Edge(input[i][0], input[i][1]));
}
let answer=0;
const uf=new UnionFind(node);
for(let i=0;i<times;++i){
  let parentOfP1=uf.find(edges[i].from);
  let parentOfP2=uf.find(edges[i].to);
  if(parentOfP1!==parentOfP2){
    uf.union(parentOfP1, parentOfP2);
  }
  else{
    console.log(i+1);
    return;
  }
}
console.log(0);