題目

Given a 2D board and a list of words from the dictionary, find all words in the board.

Each word must be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.

分析

    有一種叫boggle的遊戲

class Solution（Object):
    # @param board, a list of lists of 1 length string
    # @param word, a string
    # @return a boolean
    def findWords(self, board, word):
        def dfs(x, y, word):
            if len(word)==0: return True
            #up
            if x>0 and board[x-1][y]==word[0]:
                tmp=board[x][y]; board[x][y]='#'
                if dfs(x-1,y,word[1:]):
                    return True
                board[x][y]=tmp
            #down
            if x<len(board)-1 and board[x+1][y]==word[0]:
                tmp=board[x][y]; board[x][y]='#'
                if dfs(x+1,y,word[1:]):
                    return True
                board[x][y]=tmp
            #left
            if y>0 and board[x][y-1]==word[0]:
                tmp=board[x][y]; board[x][y]='#'
                if dfs(x,y-1,word[1:]):
                    return True
                board[x][y]=tmp
            #right
            if y<len(board[0])-1 and board[x][y+1]==word[0]:
                tmp=board[x][y]; board[x][y]='#'
                if dfs(x,y+1,word[1:]):
                    return True
                board[x][y]=tmp
            return False
                
        for i in range(len(board)):
            for j in range(len(board[0])):
                if board[i][j]==word[0]:
                    if(dfs(i,j,word[1:])):
                        return True
        return False