ABCPATH  ABC Path
You will be given a 2dimensional grid of letters. Find the length of the longest path of consecutive letters, starting at 'A'. Paths can step from one letter in the grid to any adjacent letter (horizontally, vertically, or diagonally).
For example, in the following grid, there are several paths from 'A' to 'D', but none from 'A' to 'E':
One such path is:
Input
Each test case will start with a line contains two integers H, W the height and width of the grid respectively 1 <= H, W <= 50. Then H lines follow each of W uppercase letters only. Input terminates with H = 0 and W = 0.
Output
For each test case print “Case C: X” without quotes where C is the case number starting with 1 and X is the solution.
Example
Sample Input: 4 3 ABE CFG BDH ABC 0 0 Sample Output: Case 1: 4
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me_milan_11:
20190114 09:11:03
Didn't use memo and got 2 TLEs. Then AC 

gaurav1614:
20181226 18:08:22
DP on graphs.easily solvable in O(n*m) complexity. 

manishjoshi394:
20181105 16:50:43
Simple DFS, AC in one go! :) 

joe85123:
20181021 09:08:18
BFS and DFS both work just fine! good problem to practice both 

masterchef2209:
20181011 20:38:04
recursion +memoisation 

ameyanator:
20180916 08:29:43
Nice question I started with recursion and optimized it to multisource bfs. Got a lot of TLEs in between 

nour_b3:
20180909 19:30:29
AC in one go !! 

c0der_ace:
20180705 15:23:11
Simple DFS !! Just make once used characters unusable for further times as they can never help to reach farther than they did last time ;) 

selva1996:
20180525 16:51:05
Good one Last edit: 20180526 06:23:18 

frozen7:
20180204 07:39:51
use multisource bfs 
Added by:  Ali Arous 
Date:  20111105 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 
Resource:  FCIS Local Contest 2012 