LeetCode_Word Search

二维网格单词搜索

最新推荐文章于 2025-09-08 23:34:59 发布

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最新推荐文章于 2025-09-08 23:34:59 发布

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CC 4.0 BY-SA版权

文章标签：数据结构与算法 c/c++

原文链接：http://www.cnblogs.com/graph/p/3237065.html

本文介绍了一种算法，用于判断一个给定的单词是否能在二维字符网格中找到。通过递归深度优先搜索的方法，检查所有可能的路径，确保同一个字母单元格不会被重复使用。

Given a 2D board and a word, find if the word exists in the grid.

The word can 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.

For example,
Given board =

[
  ["ABCE"],
  ["SFCS"],
  ["ADEE"]
]

word = "ABCCED", -> returns true,
word = "SEE", -> returns true,
word = "ABCB", -> returns false.

　　AC 代码：

class Solution {
public:
   bool search(vector<vector<char> > &board, const string & word, int i, int j, int index, vector<vector<bool>> &flag)
    {
          if(index == len) return true;
          //up
          if(i-1 >=0 && board[i-1][j] == word[index] && flag[i-1][j] == false) { 
             flag[i-1][j] = true;
             if(search(board, word, i-1, j,index+1, flag) )  return true;
             flag[i-1][j] = false;
          }
          //down
          if(i+1 < rows && board[i+1][j] == word[index] && flag[i+1][j] == false){
            flag[i+1][j] = true;
            if(search(board, word, i+1, j, index+1, flag)) return true;
            flag[i+1][j] = false;
          }
         //right
         if( j+1 < columns && board[i][j+1] == word[index] && flag[i][j+1] == false){
            flag[i][j+1] = true;
            if(search(board, word, i, j+1, index+1, flag)) return true;
            flag[i][j+1] = false;
         }
         //left
         if(j-1 >= 0 && board[i][j-1] == word[index] && flag[i][j-1] == false){
            flag[i][j-1] = true;
            if(search(board, word, i, j-1, index+1, flag)) return true;
            flag[i][j-1] = false;
         }
         return false;
    }
    bool exist(vector<vector<char> > &board, string word) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        rows = board.size();
        columns = board[0].size();
        len = word.size();
        if(len == 0) return true ;
        if(rows * columns < len) return false;
       
        for(int i = 0; i< rows ;i++)
            for(int j = 0; j< columns ; j++){    
                if(board[i][j] == word[0])
                {
                   vector<vector<bool>>  flag(rows, vector<bool>(columns, false)) ;
                    flag[i][j] = true;
                    if(search(board,word, i, j,1,flag)) return true;
                   // flag[i][j] = false;
                }
            }
               
        return false;
    }
private:
    int rows;
    int columns;
    int len ;
};

未AC的奇怪代码

class Solution {
public:
   bool search(vector<vector<char> > &board, const string & word, int i, int j, int index)
    {
          if(index == len) return true;
          //up
          if(i-1 >=0 && board[i-1][j] == word[index] && flag[i-1][j] == false) { 
             flag[i-1][j] = true;
             if(search(board, word, i-1, j,index+1) )  return true;
             flag[i-1][j] = false;
          }
          //down
          if(i+1 < rows && board[i+1][j] == word[index] && flag[i+1][j] == false){
            flag[i+1][j] = true;
            if(search(board, word, i+1, j, index+1)) return true;
            flag[i+1][j] = false;
          }
         //right
         if( j+1 < columns && board[i][j+1] == word[index] && flag[i][j+1] == false){
            flag[i][j+1] = true;
            if(search(board, word, i, j+1, index+1)) return true;
            flag[i][j+1] = false;
         }
         //left
         if(j-1 >= 0 && board[i][j-1] == word[index] && flag[i][j-1] == false){
            flag[i][j-1] = true;
            if(search(board, word, i, j-1, index+1)) return true;
            flag[i][j-1] = false;
         }
         return false;
    }
    bool exist(vector<vector<char> > &board, string word) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        rows = board.size();
        columns = board[0].size();
        len = word.size();
        if(len == 0) return true ;
        if(rows * columns < len) return false;
        flag.resize(rows, vector<bool>(columns, false)) ;
        for(int i = 0; i< rows ;i++)
            for(int j = 0; j< columns ; j++){    
                if(board[i][j] == word[0])
                {            
                    flag[i][j] = true;
                    if(search(board,word, i, j,1)) return true;
                    flag[i][j] = false;
                }
            }
               
        return false;
    }
private:
    vector<vector<bool>>  flag;
    int rows;
    int columns;
    int len ;
};