B. Two Buttons1400 / 简单的bfs

Posted 2021-11-11 幽殇默

https://codeforces.com/problemset/problem/520/B

#include<bits/stdc++.h>
using namespace std;
typedef long long int LL;
const int N=1e5+10;
LL n,m,dist[N];
int bfs(int n)
{
	unordered_map<int,int>mp;
	queue<int>q;
	q.push(n),mp[n]++,dist[n]=0;
	while(q.size())
	{
		int x=q.front(); q.pop();
		if(x==m) return dist[x];
		int dx[2]={-1,x};
		for(int i=0;i<2;i++)
		{
			int tempx=x+dx[i];
			if(tempx<0) continue;
			if(tempx>=N) continue;
			if(mp[tempx]) continue;
			dist[tempx]=dist[x]+1;
			q.push(tempx),mp[tempx]++;
		}
	}
}
int main(void)
{
	cin>>n>>m;
	cout<<bfs(n);
	return 0;
}