HDOJ 1195 Open the Lock bfs 双向bfs

bfs和双向bfs效率对比


bfs代码

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
int vis[10100];
struct node{
int num,dist;
};
void change(int num[4],int num1)
{
num[0]=num1/1000;
num[1]=num1/100%10;
num[2]=num1/10%10;
num[3]=num1%10;
}
int change_back(int num[4])
{
int sum=0;
for(int i=0;i<4;i++)
sum=sum*10+num[i];
return sum;
}
int solve(int num1,int num2)
{
memset(vis,0,sizeof(vis));
int num[4];
node s;
s.num=num1;
s.dist=0;
queue<node> q;
q.push(s);
while(!q.empty())
{
node m=q.front();q.pop();
if(m.num==num2) return m.dist;
for(int i=0;i<4;i++)
{
change(num,m.num);
num[i]++;
if(num[i]==10) num[i]=1;
int p1=change_back(num);
if(!vis[p1])
{
vis[p1]=1;
node l;
l.num=p1;
l.dist=m.dist+1;
q.push(l);
}
change(num,m.num);
num[i]--;
if(num[i]==0) num[i]=9;
int p2=change_back(num);
if(!vis[p2])
{
vis[p2]=1;
node l;
l.num=p2;
l.dist=m.dist+1;
q.push(l);
}
}
for(int i=0;i<3;i++)
{
change(num,m.num);
int t=num[i];num[i]=num[i+1];num[i+1]=t;
int p=change_back(num);
if(!vis[p])
{
vis[p]=1;
node l;
l.num=p;
l.dist=m.dist+1;
q.push(l);
}
}
}
return 0;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
int num1,num2;
scanf("%d%d",&num1,&num2);
int ans;
ans=solve(num1,num2);
printf("%d\n",ans);
}
return 0;
}

双向bfs

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
int vis[10100];
int dist[10010];
void change(int num[4],int num1)
{
num[0]=num1/1000;
num[1]=num1/100%10;
num[2]=num1/10%10;
num[3]=num1%10;
}
int change_back(int num[4])
{
int sum=0;
for(int i=0;i<4;i++)
sum=sum*10+num[i];
return sum;
}
int solve(int num1,int num2)
{
memset(vis,0,sizeof(vis));
memset(dist,-1,sizeof(dist));
dist[num1]=0;
dist[num2]=0;
vis[num1]=1;
vis[num2]=2;
queue<int> q;
q.push(num1);
q.push(num2);
int num[4];
while(!q.empty())
{
int x=q.front();q.pop();
for(int i=0;i<4;i++)
{
change(num,x);
num[i]++;
if(num[i]==10) num[i]=1;
int p1=change_back(num);
if(vis[p1]&&vis[x]!=vis[p1]) return dist[x]+dist[p1]+1;
if(!vis[p1])
{
vis[p1]=vis[x];
dist[p1]=dist[x]+1;
q.push(p1);
}
change(num,x);
num[i]--;
if(num[i]==0) num[i]=9;
int p2=change_back(num);
if(vis[p2]&&vis[p2]!=vis[x]) return dist[x]+dist[p2]+1;
if(!vis[p2])
{
vis[p2]=vis[x];
dist[p2]=dist[x]+1;
q.push(p2);
}
}
for(int i=0;i<3;i++)
{
change(num,x);
int t=num[i];num[i]=num[i+1];num[i+1]=t;
int p=change_back(num);
if(vis[p]&&vis[x]!=vis[p]) return dist[x]+dist[p]+1;
if(!vis[p])
{
vis[p]=vis[x];
dist[p]=dist[x]+1;
q.push(p);
}
}
}
return 0;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
int num1,num2;
scanf("%d%d",&num1,&num2);
int ans;
ans=solve(num1,num2);
printf("%d\n",ans);
}
return 0;
}