[LeetCode] Word SearchGiven 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.递归Java:public class Solution {    public boolean exist(char[][] board, String word) {        // Start typing your Java solution below        // DO NOT write main() function        if(word.length() == 0)   return true;        int h = board.length;        if(h == 0)    return false;        int w = board[0].length;        boolean[][] flag = new boolean[h][w];                for(int i = 0; i < h; i++){            for(int j = 0; j < w; j++){                if(word.charAt(0) == board[i][j]){                    if(func(board, word, 0, w, h, j, i, flag)) return true;                }            }        }                return false;    }        public boolean func(char[][] board, String word, int spos, int w, int h, int x, int y, boolean[][] flag){        if(spos == word.length())  return true;        if(x < 0 || x >= w || y < 0 || y >= h)   return false;        if(flag[y][x] || board[y][x] != word.charAt(spos))   return false;                flag[y][x] = true;                // up        if(func(board, word, spos + 1, w, h, x, y-1, flag)){            return true;        }        // down        if(func(board, word, spos + 1, w, h, x, y+1, flag)){            return true;        }        // left        if(func(board, word, spos + 1, w, h, x-1, y, flag)){            return true;        }        // right        if(func(board, word, spos + 1, w, h, x+1, y, flag)){            return true;        }                flag[y][x] = false;                return false;    }}c++class Solution {public:    bool exist(vector
     
      
        > &board, string word) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(word.size() == 0)  return true;        int h = board.size();        if(h == 0)   return false;        int w = board[0].size();        vector
       
        
          > flag(h, vector
         
          (w, false));                for(int i = 0; i < h; i++){            for(int j = 0; j < w; j++){                if(board[i][j] == word[0]){                    if(func(board, word, w, h, j, i, 0, flag))   return true;                }            }        }        return false;    }        bool func(vector
          
           
             > board, string word, int w, int h, int x, int y, int spos, vector
            
             
               > flag){ if(spos == word.size()) return true; if(x < 0 || x >= w || y < 0 || y >= h) return false; if(flag[y][x] || word[spos] != board[y][x]) return false; flag[y][x] = true; // up if(func(board, word, w, h, x, y - 1, spos + 1, flag)){ return true; } if(func(board, word, w, h, x, y + 1, spos + 1, flag)){ return true; } if(func(board, word, w, h, x - 1, y, spos + 1, flag)){ return true; } if(func(board, word, w, h, x + 1, y, spos + 1, flag)){ return true; } flag[y][x] = false; return false; }};