[LeetCode]Word Search-优快云博客

本文链接：https://blog.youkuaiyun.com/CiaoLiang/article/details/45115751

本文探讨了如何使用深度优先搜索（DFS）算法，在给定的二维网格中查找特定单词是否存在，通过相邻单元格的字母构建单词，同时强调了算法的边界条件处理和避免重复使用同一单元格的重要性。

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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.

LeetCode Source

思路：典型的DFS算法，每次从string开始搜寻。

特别注意边界条件，每次搜寻时作标记，如果搜寻没有成功的话，标志消除。

class Solution {
public:
    bool exist(vector<vector<char> > &board, string word) {
        for(int i=0;i<board.size();++i){
            for(int j=0;j<board[0].size();++j){
                if(dfs(board,i,j,word.begin(),word.end()))
                    return true;
            }
        }
        return false;
    }
    bool dfs(vector<vector<char> >&board,int m,int n,string::iterator it,string::iterator end){
        if(m<0||n<0||m>board.size()-1||n>board[0].size()-1||board[m][n]!=*it)
            return false;
        if(board[m][n]==*it&&it+1==end)
            return true;
        char temp = board[m][n];
        board[m][n] = '0'; //做标记
    if(dfs(board,m-1,n,it+1,end)||dfs(board,m+1,n,it+1,end)||dfs(board,m,n+1,it+1,end)||dfs(board,m,n-1,it+1,end))
        {
            return true;
        }
        board[m][n] = temp; //没有搜寻到标记清楚，没有这条语句会报错
        return false;
    }
};