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POJ 3278 Catch That Cow
Catch That Cow
Time Limit: 2000MS | Memory Limit: 65536K | |
Total Submissions: 43517 | Accepted: 13549 |
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.
/*****************************************************/ /**** POJ 3278 Catch That Cow ******/ /**** Wangguoliang @Greenday ******/ /**** 2014-5-12 ******/ #include<stdio.h> #include<iostream> #include<queue> #include<string.h> using namespace std; int visit[200001];//1为遍历过,0为未遍历 int n,m,flag; struct node //定义结点 { int pi; int step; }; queue<node>Q;//定义对列 Q void BFS() //广度优先搜索 { node p,q; int i,j; p.pi=n,p.step=0; Q.push(p); //入队 while(!Q.empty())//判断是否队列已空 { p=Q.front(); //返回队列第一个元素 Q.pop(); //函数删除队列的一个元素 if(p.pi==m) //找到终点,结束 { flag=p.step; return ; } p.step++; //未找到步加1 if(p.pi<m&&!visit[p.pi]) //直接乘以2 { q=p; q.pi*=2; Q.push(q); } if(p.pi>0&&!visit[p.pi])//判断是否大于0,然后-- { q=p; q.pi--; Q.push(q); } if(!visit[p.pi])//直接++,然后把这个点标记为遍历过 { q=p; q.pi++; Q.push(q); visit[p.pi]=1; } } } int main() { while(scanf("%d%d",&n,&m)!=EOF) { memset(visit,0,sizeof(visit));//去除标记清0 flag=0; BFS(); printf("%d\n",flag); //while(!Q.empty())//清空队列 Q.pop(); } return 0; } /* #include<iostream> #include<queue> using namespace std; int a[100001],b[100001]; int main() { int m,n,y; queue<int>x;//建立名为x的队列 cin>>m>>n; x.push(m);//在队列后加入m a[m]=0; while(x.size()!=0)//队列大小不为0 { y=x.front();//y取队列首位 x.pop();//去掉队列首位 b[y]=1; if(y==n) break; if(y-1>=0&&b[y-1]==0) { x.push(y-1); a[y-1]=a[y]+1; b[y-1]=1; } if(y+1<=100000&&b[y+1]==0) { x.push(y+1); a[y+1]=a[y]+1; b[y+1]=1; } if(2*y<=100000&&b[2*y]==0) { x.push(2*y); a[2*y]=a[y]+1; b[2*y]=1; } } cout<<a[y]<<endl; return 0; } /* //搜索的百度的不用stl 的算法 memory 980K time 16Ms #include <iostream> #include <cstring> #include <cmath> #include <cstdlib> #include <algorithm> #include <string> #include <cstdio> #include <climits> using namespace std; bool data[100005] = {0}; int que[100005] = {0}; int tnum[100005] = {0}; void bfs(int n, int k) { int front = 0, rear = 0; que[0] = n; data[n] = true; tnum[0] = 0; rear++; while (front != rear) { int t = que[front]; int tn = tnum[front]; if (t == k) { printf("%d\n", tn); return; } if (t > 0 && !data[t-1]) { data[t-1] = true; que[rear] = t-1; tnum[rear] = tn+1; rear++; } if (t < 100000 && !data[t+1]) { data[t+1] = true; que[rear] = t+1; tnum[rear] = tn+1; rear++; } if (t <= 50000 && !data[t*2]) { data[t*2] = true; que[rear] = t*2; tnum[rear] = tn+1; rear++; } front++; } printf("0\n"); } int main() { int n, k; scanf("%d%d", &n, &k); memset(data, 0, sizeof(data)); bfs(n, k); return 0; }
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