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Word Search - Leetcode 79 - Python

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.


class Solution:

    def exist(self, b: List[List[str]], w: str) -> bool:

        row, col = len(b), len(b[0])

        p = set()

        

        def dfs(r, c, i):

            if i == len(w):

                return True

            

            if (

                r<0 or 

                c<0 or

                r>=row or

                c>=col or

                w[i]!=b[r][c] or

                (r,c) in p  

               ) : return False

            

            p.add((r,c))

            

            ans = (dfs(r+1,c,i+1) or

                  dfs(r-1,c,i+1) or

                  dfs(r,c+1,i+1) or

                  dfs(r,c-1,i+1))

            

            p.remove((r,c))

            return ans

        

        for r in range(row):

            for c in range(col):

                if dfs(r,c,0): return True

        return False

             

Explaination :



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