学步园

#include<stdio.h>
#include<stack>
#include<queue>
#include<string.h>
using namespace std;
int state[200010];
int N,K;
int dir[3][2]={{1,-1},{1,1},{2,0}};
queue<int> record;
int BFS(){
    if(N==K) return 0;
    record.push(N);
    state[N]=1;
    while(!record.empty()){
        int cur,temp;
        cur=record.front();
        record.pop();
        for(int a=0;a<3;a++){
            temp=cur*dir[a][0]+dir[a][1];
            if(temp==K) return state[cur];
            if(temp>=0&&temp<200010){
                if(!state[temp]){
                    record.push(temp);
                    state[temp]=state[cur]+1;
                }
            }
        }
    }
}
int main(){
    memset(state,0,sizeof(state));
    cin>>N>>K;
    int step;
    step=BFS();
    cout<<step<<endl;
    return 0;
}