HERDING  Herding
Oh no! A number of stray cats have been let loose in the city, and as the City Cat Catcher, you have been assigned the vital task of retrieving all of the cats. This is an ideal opportunity to test your latest invention, a cat trap which is guaranteed to retrieve every cat which walks into a squareshaped subsection of the city.
Fortunately, you have the assistance of one of the world's foremost cat psychologists, who has the amazing ability of predicting, given a square subsection of the city, exactly which of the four cardinal directions (north, east, south or west) the cat will head. While this information is handy, you still don't know where all the cats currently are.
In order to prove the costeffectiveness of your method to the City it would, of course, be important to minimize the number of traps used.
Input
The input will begin with a line consisting of two numbers n and m, separated by a space (1 ≤ n, m ≤ 1000). The city will be an n x m grid of square subsections. The next n lines will each consist of a string of length m, consisting of the letters 'N', 'E', 'S', or 'W', representing north, east, south and west, respectively. (The first character of the first line will be the northwesternmost point.) The direction in the square is the direction which cats will head if they are in that square. The cat psychologist assures you that cats have no interest in leaving the city.
Output
Output the minimum number of traps needed.
Example
Input: 3 4 SWWW SEWN EEEN Output: 2
hide comments
yuvrajsharma:
20201003 18:37:16
AC in first go


vishalshrm539:
20200822 20:19:06
BFS! 

vickyvanshaj:
20200609 21:05:44
AC in one go!! 

shubham_it_bit:
20200505 17:44:55
good one .. a bit different and interesting problem if done with dfs 

smug__face:
20200324 19:15:10
4 4


dkkv0000:
20200119 14:01:47
good problem on dfs 3rd attempt AC 

sohit5012:
20190714 10:07:57
Use DFS , for some reason Bfs gives TLE, maybe its the overhead of using a queue. 

haiderbaig:
20190314 14:13:34
Solved by creating a 2D array and traversing it according to the direction mentioned on the cells. Also have to keep track of visited cells.


ab_biswas09:
20190116 20:29:47
Solved using DFS by keeping track of visited nodes in the current recursion stack 

suyashky:
20181225 20:39:43
Similar questions to try (SPOJ questions):

Added by:  JaceTheMindSculptor 
Date:  20090407 
Time limit:  0.902s1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: C99 ERL JSRHINO 
Resource:  Canadian Computing Competition 2008 Stage 2 Day 2 Problem D 