hdu（2717）Catch That Cow

运用优先队列把所有情况都入队，然后取出步数最少的。。

#include"stdio.h"

#include"string.h"

int visit[110000];

#include"queue"

using namespace std;

int n,m;

struct point

{

int x,step;

friend bool operator<(point a,point b)

{

return a.step>b.step;

}

};

int dfs()

{

priority_queue<point>q;

point cur,next;

cur.x=n;

cur.step=0;

visit
=1;

q.push(cur);

while(!q.empty())

{

next=q.top();

q.pop();

if(next.x==m)

return next.step;

cur.x=next.x+1;

if(cur.x<=100000&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

cur.x=next.x-1;

if(cur.x>=0&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

cur.x=next.x*2;

if(cur.x<=100000&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

}

}

int main()

{

while(scanf("%d%d",&n,&m)!=EOF)

{

memset(visit,0,sizeof(visit));

printf("%d\n",dfs());

}

return 0;

}

这个队列更省时。。

#include"stdio.h"

#include"string.h"

int visit[110000];

#include"queue"

using namespace std;

int n,m;

struct point

{

int x,step;

};

int dfs()

{

queue<point>q;

point cur,next;

cur.x=n;

cur.step=0;

visit
=1;

q.push(cur);

while(!q.empty())

{

next=q.front();

q.pop();

if(next.x==m)

return next.step;

cur.x=next.x+1;

if(cur.x<=100000&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

cur.x=next.x-1;

if(cur.x>=0&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

cur.x=next.x*2;

if(cur.x<=100000&&!visit[cur.x])

{

visit[cur.x]=1;

cur.step=next.step+1;

q.push(cur);

}

}

}

int main()

{

while(scanf("%d%d",&n,&m)!=EOF)

{

memset(visit,0,sizeof(visit));

printf("%d\n",dfs());

}

return 0;

}