Robot Motion
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 10072 Accepted Submission(s): 4697
Problem Description
A robot has been programmed to follow the instructions in its path. Instructions for the next direction the robot is to move are laid down in a grid. The possible instructions are
N north (up the page)
S south (down the page)
E east (to the right on the page)
W west (to the left on the page)
For example, suppose the robot starts on the north (top) side of Grid 1 and starts south (down). The path the robot follows is shown. The robot goes through 10 instructions in the grid before leaving the grid.
Compare what happens in Grid 2: the robot goes through 3 instructions only once, and then starts a loop through 8 instructions, and never exits.
You are to write a program that determines how long it takes a robot to get out of the grid or how the robot loops around.
Input
There
will be one or more grids for robots to navigate. The data for each is
in the following form. On the first line are three integers separated by
blanks: the number of rows in the grid, the number of columns in the
grid, and the number of the column in which the robot enters from the
north. The possible entry columns are numbered starting with one at the
left. Then come the rows of the direction instructions. Each grid will
have at least one and at most 10 rows and columns of instructions. The
lines of instructions contain only the characters N, S, E, or W with no
blanks. The end of input is indicated by a row containing 0 0 0.
Output
For
each grid in the input there is one line of output. Either the robot
follows a certain number of instructions and exits the grid on any one
the four sides or else the robot follows the instructions on a certain
number of locations once, and then the instructions on some number of
locations repeatedly. The sample input below corresponds to the two
grids above and illustrates the two forms of output. The word "step" is
always immediately followed by "(s)" whether or not the number before it
is 1.
Sample Input
3 6 5
NEESWE
WWWESS
SNWWWW
4 5 1
SESWE
EESNW
NWEEN
EWSEN
0 0
DFS简单题
1 #include<iostream> 2 #include<cstdio> 3 #include<cmath> 4 #include<cstring> 5 #include<algorithm> 6 #include<queue> 7 #include<map> 8 #include<set> 9 #include<vector> 10 #include<cstdlib> 11 #include<string> 12 #define eps 0.000000001 13 typedef long long ll; 14 typedef unsigned long long LL; 15 using namespace std; 16 const int N=100; 17 char mp[N][N]; 18 int visited[N][N]; 19 int m,n; 20 int flag; 21 int step,loopstep; 22 void DFS(int x,int y){ 23 if(x<0||x>=n||y<0||y>=m){ 24 return ; 25 } 26 if(visited[x][y]!=0){ 27 flag=1; 28 loopstep=step-visited[x][y]+1; 29 step=visited[x][y]-1; 30 return ; 31 } 32 step++; 33 visited[x][y]=step; 34 if(mp[x][y]=='N')DFS(x-1,y); 35 else if(mp[x][y]=='S')DFS(x+1,y); 36 else if(mp[x][y]=='E')DFS(x,y+1); 37 else if(mp[x][y]=='W')DFS(x,y-1); 38 } 39 int main(){ 40 while(scanf("%d%d",&n,&m)!=EOF){ 41 if(n==0&&m==0)break; 42 int k; 43 scanf("%d",&k); 44 flag=0; 45 for(int i=0;i<n;i++)scanf("%s",mp[i]); 46 loopstep=step=0; 47 memset(visited,0,sizeof(visited)); 48 DFS(0,k-1); 49 if(flag==0) printf("%d step(s) to exit ", step); 50 else 51 printf("%d step(s) before a loop of %d step(s) ", step,loopstep); 52 53 } 54 }
Sample Output
10 step(s) to exit
3 step(s) before a loop of 8 step(s)