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HDU2717-Catch That Cow (BFS入门)

题目传送门:http://acm.hdu.edu.cn/showproblem.php?pid=2717

Catch That Cow

Time Limit: 5000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 14880    Accepted Submission(s): 4495


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?
 

 

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.
 
题意:
从a走到b,你可以向前走一步,向后走一步或者走a*2步,求最少多少步
 
 1 #include<stdio.h> 2 #include<string.h> 3 #include<queue> 4 using namespace std; 5 int v[100010],t[100010]; 6 int main() 7 { 8     int n,a,b,i,f; 9     while(scanf("%d%d",&a,&b)!=EOF)10     {11         memset(t,0,sizeof(t));12         memset(v,0,sizeof(v));13         queue<int > q;14         q.push(a);15         v[a]=1;16         if(a==b)17         {18             printf("0\n");19             continue;20         }21         while(!q.empty())22         {23             int ll=q.front(),r=ll-1,l=ll+1,z=ll*2;24             q.pop();25             //printf("ll=%d\n",ll);26             if(z>=0&&z<=100000&&!v[z])27             {28                 q.push(z);29                 v[z]=v[ll]+1;30             //    printf("v[z]=%d z=%d\n",v[z],z);31             }32             if(l>=0&&l<=100000&&!v[l])33             {34                 q.push(l);35                 v[l]=v[ll]+1;36                 //    printf("v[l]=%d l=%d\n",v[l],l);37             }38             if(r>=0&&r<=100000&&!v[r])39             {40                 q.push(r);41                 v[r]=v[ll]+1;42                 //    printf("v[r]=%d r=%d\n",v[r],r);43              }44              45              if(l==b||r==b||z==b)46              {47              48                  break;49              }50                   51         }52         53         printf("%d\n",v[b]-1);54         55     }56     return 0;57     58  } 

 

HDU2717-Catch That Cow (BFS入门)