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Word Search

Tags : array, matrix, leetcode, cpp, medium

Problem Statement - link #

Given an m x n grid of characters board and a string word, return true if word exists in the grid.

The word can be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once.

Examples #

Example 1:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCCED"
Output: true

Example 2:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "SEE"
Output: true

Example 2:

Input: board = [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]], word = "ABCB"
Output: false

Constraints #

Follow up: Could you use search pruning to make your solution faster with a larger board?

Solutions #

class Solution {
public:
    bool mnk(vector<vector<char>>& board, string word, int i, int j, int wi){
        
        if( wi == word.length()) return true;
        
        if( i >= board.size() || j >= board[0].size() || i<0 || j<0|| board[i][j] == '*' || board[i][j] != word[wi]  ) return false;
        
        char curr = board[i][j];
        board[i][j] = '*';
        
        bool ans = ( mnk(board,word,i,j-1,wi+1) || mnk(board,word,i,j+1,wi+1) || mnk(board,word,i-1,j,wi+1) || mnk(board,word,i+1,j,wi+1) );
        board[i][j] = curr;
        return ans;
        
    }
    
    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(board[i][j] == word[0]){
                    
                    if(mnk(board, word, i, j, 0))
                        return true;
                }
            }
        }
        return false;
    }
};