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题目
单词可以由按顺序的相邻单元的字母组成，其中相邻单元指的是水平或者垂直方向相邻。每个单元中的字母最多只能使用一次。
给出board =
[
"ABCE",
"SFCS",
"ADEE"
]
word = "ABCCED"， ->返回 true,
word = "SEE"，-> 返回 true,
word = "ABCB"， -> 返回 false.
解题
直接深度搜索
public class Solution { public boolean exist(char[][] board, String word) { return method(board,word); } public boolean method(char[][] board,String word){ int row = board.length; int col = board[0].length; boolean[][] visited = new boolean[row][col]; for(int i=0;i<row;i++) for(int j=0;j<col;j++) if(dfs(board,visited,i,j,0,word)) return true; return false; } public boolean dfs(char[][] board,boolean[][] visited,int row,int col,int index,String word){ if(word.length() == index){ return true; } if(row<0 || col<0||row>=board.length || col>=board[0].length) return false; char ch = word.charAt(index); if(!visited[row][col] && ch == board[row][col]){ visited[row][col] = true; boolean res = dfs(board,visited,row-1,col,index+1,word)|| dfs(board,visited,row+1,col,index+1,word) ||dfs(board,visited,row,col-1,index+1,word)|| dfs(board,visited,row,col+1,index+1,word); visited[row][col] = false; return res; } return false; } }
修改原始数组，降低空间复杂度
public class Solution { /** * @param board: A list of lists of character * @param word: A string * @return: A boolean */ public boolean exist(char[][] board, String word) { // write your code here return method(board,word); } public boolean method(char[][] board,String word){ int row = board.length; int col = board[0].length; for(int i=0;i<row;i++) for(int j=0;j<col;j++){ if(dfs(board,i,j,0,word)) return true; } return false; } public boolean dfs(char[][] board,int row,int col,int index,String word){ if(word.length() == index){ return true; } if(row<0 || col<0||row>=board.length || col>=board[0].length) return false; char ch = word.charAt(index); if(board[row][col]!=‘+‘ && ch == board[row][col]){ char c = board[row][col]; board[row][col]=‘+‘; boolean res = dfs(board,row-1,col,index+1,word)|| dfs(board,row+1,col,index+1,word) ||dfs(board,row,col-1,index+1,word)|| dfs(board,row,col+1,index+1,word); board[row][col] = c; return res; } return false; } }
Python
class Solution(object): def exist(self, board, word): """ :type board: List[List[str]] :type word: str :rtype: bool """ for i in xrange(len(board)): for j in xrange(len(board[0])): if self.dfs(board,i,j,word,0): return True return False def dfs(self,board,row,col,word,index): if index == len(word): return True if row<0 or col<0 or row>=len(board) or col>=len(board[0]): return False ch = word[index] res = False if(board[row][col]!=‘+‘ and board[row][col] ==ch): c = board[row][col] board[row][col] = ‘+‘ res = self.dfs(board,row-1,col,word,index+1) or self.dfs(board,row,col-1,word,index+1) or self.dfs(board,row+1,col,word,index+1) or self.dfs(board,row,col+1,word,index+1) if res: return res else: board[row][col] = c return False
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原文地址：http://www.cnblogs.com/theskulls/p/5157488.html
