首页 > 代码库 > BZOJ1646: [Usaco2007 Open]Catch That Cow 抓住那只牛
BZOJ1646: [Usaco2007 Open]Catch That Cow 抓住那只牛
1646: [Usaco2007 Open]Catch That Cow 抓住那只牛
Time Limit: 5 Sec Memory Limit: 64 MBSubmit: 634 Solved: 310
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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
Farmer John starts at point 5 and the fugitive cow is at point 17.
Sample Output
OUTPUT DETAILS:
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.
HINT
Source
Silver
1 #include<cstdio> 2 #include<cstdlib> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 #include<iostream> 7 #include<vector> 8 #include<map> 9 #include<set>10 #include<queue>11 #include<string>12 #define inf 100000000013 #define maxn 200000+100014 #define maxm 40000015 #define eps 1e-1016 #define ll long long17 #define pa pair<int,int>18 using namespace std;19 inline int read()20 {21 int x=0,f=1;char ch=getchar();22 while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}23 while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}24 return x*f;25 }26 struct edge{int go,next,w;}e[2*maxm];27 int n,s,t,tot,q[maxn],d[maxn],head[maxn];28 bool v[maxn];29 void ins(int x,int y)30 {31 e[++tot].go=y;e[tot].next=head[x];head[x]=tot;32 }33 void insert(int x,int y)34 {35 ins(x,y);ins(y,x);36 }37 void spfa()38 {39 for(int i=0;i<=n;++i) d[i]=inf;40 memset(v,0,sizeof(v));41 int l=0,r=1,x,y;q[1]=s;d[s]=0;42 while(l!=r)43 {44 x=q[++l];if(l==maxn)l=0;v[x]=0;45 for(int i=head[x];i;i=e[i].next)46 if(d[x]+1<d[y=e[i].go])47 {48 d[y]=d[x]+1;49 if(!v[y]){v[y]=1;q[++r]=y;if(r==maxn)r=0;}50 }51 }52 53 }54 int main()55 {56 freopen("input.txt","r",stdin);57 freopen("output.txt","w",stdout);58 s=read();t=read();59 if(s>=t){printf("%d\n",abs(t-s));return 0;}60 else n=t+abs(t-s)+1;61 for(int i=0;i<n;i++)insert(i,i+1);62 for(int i=1;i<=n/2;i++)ins(i,i<<1);63 spfa();64 printf("%d\n",d[t]);65 return 0;66 }
BZOJ1646: [Usaco2007 Open]Catch That Cow 抓住那只牛