bfs广搜 题解 100% AC

#include <bits/stdc++.h>
using namespace std;
int n,k,sum,a[200010];
void bfs(int x){
    queue<int>q;
    q.push(x);
    a[x]=0;
    while(!q.empty()){
        int r=q.front();
        q.pop();
        if(r==k){
            cout<<a[k];
            return;
        }else{
            if(a[r-1]==0&&r>=1){
                a[r-1]=a[r]+1;
                q.push(r-1);
            }
            if(a[r+1]==0&&(r+1)<=100000){
                a[r+1]=a[r]+1;
                q.push(r+1);
            }
            if(a[r*2]==0&&r*2<=100000){
                a[r*2]=a[r]+1;
                q.push(2*r);
            }
        }
    }
}
int main(){
    cin>>n>>k;
    bfs(n);
    return 0;
}