[BOJ] 13549번 숨바꼭질3

#include < iostream>
#include < queue>

using namespace std;

int n,k;

bool check[200001];
int dis[200001];

void bfs(){
    queue< int> q0;
    queue< int> q1;

    q0.push(n);
    check[n] = true;
    dis[n] = 0;

    while(!q0.empty()){
        int start = q0.front();
        q0.pop();

        for(int i=0;i<3;i++){
            int node;
            if(i==0){
                node = start*2;
            }else if(i==1){
                node = start-1;
            }else{
                node = start+1;
            }

            if(node<0 || node>200000){
                continue;
            }

            if(check[node] == false){
                if(i==0){
                    q0.push(node);
                    check[node] = true;
                    dis[node] = dis[start];
                }else{
                    q1.push(node);
                    check[node] = true;
                    dis[node] = dis[start] + 1;
                }
            }
        }

        if(q0.empty()){
            q0 = q1;
            q1 = queue();
        }
    }


}

int main()
{
    cin>>n>>k;

    bfs();

    cout<<dis[k]<<endl;

    return 0;
}

https://www.acmicpc.net/problem/13549

13549번: 숨바꼭질 3