79. Word Search

Depth first search , recursion

class Solution(object):
    def exist(self, board, word):
        """
        :type board: List[List[str]]
        :type word: str
        :rtype: bool
        """
        visited=[[False for j in xrange(len(board[0]))]for i in xrange(len(board))]
        for i in xrange(len(board)):
            for j in xrange(len(board[0])):
                if self.recursion(board,word,visited,0,i,j):
                    return True 
        return False 
        
    def recursion(self,board,word,visited,cur,i,j):
        if cur==len(word): return True 
        
        if i<0 or i>=len(board) or j<0 or j>=len(board[0]) or visited[i][j] or board[i][j]!=word[cur]:
            return False
        visited[i][j]=True
        
        result=self.recursion(board,word,visited,cur+1,i+1,j) or \
                self.recursion(board,word,visited,cur+1,i-1,j) or \
                self.recursion(board,word,visited,cur+1,i,j+1) or\
                self.recursion(board,word,visited,cur+1,i,j-1) 
        visited[i][j]=False
        
        return result