题目地址：Catch That Cow
题目大意：
一位农夫追赶一头牛，题目给出农夫和牛的坐标分别为N,K。农夫可以通过坐标的加一或减一也可以坐标乘以2。问你最少多少步到达牛的坐标。
解题思路;
简单BFS。
代码:
1 #include <algorithm> 2 #include <iostream> 3 #include <sstream> 4 #include <cstdlib> 5 #include <cstring> 6 #include <cstdio> 7 #include <string> 8 #include <bitset> 9 #include <vector> 10 #include <queue> 11 #include <stack> 12 #include <cmath> 13 #include <list> 14 //#include <map> 15 #include <set> 16 using namespace std; 17 /***************************************/ 18 #define ll long long 19 #define int64 __int64 20 #define PI 3.1415927 21 /***************************************/ 22 const int INF = 0x7f7f7f7f; 23 const double eps = 1e-8; 24 const double PIE=acos(-1.0); 25 const int d1x[]= {0,-1,0,1}; 26 const int d1y[]= {-1,0,1,0}; 27 const int d2x[]= {0,-1,0,1}; 28 const int d2y[]= {1,0,-1,0}; 29 const int fx[]= {-1,-1,-1,0,0,1,1,1}; 30 const int fy[]= {-1,0,1,-1,1,-1,0,1}; 31 const int dirx[]= {-1,1,-2,2,-2,2,-1,1}; 32 const int diry[]= {-2,-2,-1,-1,1,1,2,2}; 33 /*vector <int>map[N];map[a].push_back(b);int len=map[v].size();*/ 34 /***************************************/ 35 void openfile() 36 { 37 freopen("data.in","rb",stdin); 38 freopen("data.out","wb",stdout); 39 } 40 priority_queue<int> qi1; 41 priority_queue<int, vector<int>, greater<int> >qi2; 42 /**********************华丽丽的分割线,以上为模板部分*****************/ 43 int vis[200009],cnt[200009]; 44 int BFS(int n,int k) 45 { 46 queue<int >Q; 47 Q.push(n); 48 int v; 49 while(!Q.empty()) 50 { 51 v=Q.front(); 52 Q.pop(); 53 if (v==k) 54 return cnt[k]; 55 if (v<100005&&v>-2) 56 { 57 if (!vis[v-1]) 58 { 59 Q.push(v-1); 60 if (!cnt[v-1]) 61 cnt[v-1]=cnt[v]+1; 62 vis[v-1]=1; 63 } 64 if (!vis[v+1]) 65 { 66 Q.push(v+1); 67 if (!cnt[v+1]) 68 cnt[v+1]=cnt[v]+1; 69 vis[v+1]=1; 70 } 71 if (!vis[v*2]) 72 { 73 Q.push(v*2); 74 if (!cnt[v*2]) 75 cnt[v*2]=cnt[v]+1; 76 vis[v*2]=1; 77 } 78 } 79 } 80 return 0; 81 } 82 int main() 83 { 84 85 int n,k,sum; 86 while(scanf("%d%d",&n,&k)!=EOF) 87 { 88 memset(vis,0,sizeof(vis)); 89 memset(cnt,0,sizeof(cnt)); 90 sum=BFS(n,k); 91 printf("%d ",sum); 92 } 93 return 0; 94 }