HDU 2727 Catch That Cow
Catch That Cow
Time Limit: 5000/2000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 5457 Accepted Submission(s): 1740
Problem Description
Farmer John has been informed of the location of a fugitive cow and wants to catch her immediately. He starts at a point N (0 ≤ N ≤ 100,000) on a number line and the cow is at a point K (0 ≤ K ≤ 100,000) on the same number line. Farmer John has two modes of transportation: walking and teleporting.
* Walking: FJ can move from any point X to the points X - 1 or X + 1 in a single minute * Teleporting: FJ can move from any point X to the point 2 × X in a single minute.
If the cow, unaware of its pursuit, does not move at all, how long does it take for Farmer John to retrieve it?
* Walking: FJ can move from any point X to the points X - 1 or X + 1 in a single minute * Teleporting: FJ can move from any point X to the point 2 × X in a single minute.
If the cow, unaware of its pursuit, does not move at all, how long does it take for Farmer John to retrieve it?
Input
Line 1: Two space-separated integers: N and K
Output
Line 1: The least amount of time, in minutes, it takes for Farmer John to catch the fugitive cow.
Sample Input
5 17
Sample Output
4
Hint
The fastest way for Farmer John to reach the fugitive cow is to move along the following path: 5-10-9-18-17, which takes 4 minutes.Source
Recommend
teddy
思路:BFS + 剪枝,我是一坑货,剪枝只会皮毛
代码:
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
using namespace std;
int n,k;
int map[100010];
struct Node
{
int x;
int step;
bool operator < (const Node &t) const
{
return t.step < step;
}
}info;
int BFS()
{
priority_queue < Node > q;
info.x = n;
info.step = 0;
q.push(info);
map[info.x] = 1;
while(!q.empty())
{
Node boss;
boss = q.top();
q.pop();
if(boss.x == k)
return boss.step;
int a = boss.x;
int step = boss.step;
//printf("%d %d\n",a,step);
if(a * 2 <= 100000 && a < k && map[a * 2] == 0)
{
info.x = a * 2;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
if(a - 1 >= 0 && map[a - 1] == 0)
{
info.x = a - 1;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
if(a + 1 <= 100000 && map[a + 1] == 0)
{
info.x = a + 1;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
}
}
int main()
{
while(~scanf("%d%d",&n,&k))
{
memset(map,0,sizeof(map));
printf("%d\n",BFS());
}
}
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <queue>
using namespace std;
int n,k;
int map[100010];
struct Node
{
int x;
int step;
bool operator < (const Node &t) const
{
return t.step < step;
}
}info;
int BFS()
{
priority_queue < Node > q;
info.x = n;
info.step = 0;
q.push(info);
map[info.x] = 1;
while(!q.empty())
{
Node boss;
boss = q.top();
q.pop();
if(boss.x == k)
return boss.step;
int a = boss.x;
int step = boss.step;
//printf("%d %d\n",a,step);
if(a * 2 <= 100000 && a < k && map[a * 2] == 0)
{
info.x = a * 2;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
if(a - 1 >= 0 && map[a - 1] == 0)
{
info.x = a - 1;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
if(a + 1 <= 100000 && map[a + 1] == 0)
{
info.x = a + 1;
info.step = step + 1;
q.push(info);
map[info.x] = 1;
//printf("%d %d\n",info.x,info.step);
if(info.x == k)
return info.step;
}
}
}
int main()
{
while(~scanf("%d%d",&n,&k))
{
memset(map,0,sizeof(map));
printf("%d\n",BFS());
}
}