working solution

problem1.py

@@ -0,0 +1,54 @@
+# problem 1 
+
+# https://leetcode.com/problems/n-queens/
+
+class Solution:
+
+    def helper(self,row,n):
+        if row == n:
+            total_arr = []
+            for i in range(n):
+                row_arr = []
+                for j in range(n):
+                    if self.board[i][j]:
+                        row_arr.append('Q')
+                    else:
+                        row_arr.append('.')
+                total_arr.append(''.join(row_arr))
+            self.final_arr.append(total_arr)
+            return
+        for j in range(n):
+            if self.isValid(row,j,n):
+                self.board[row][j] = True 
+                self.helper(row+1,n)
+                self.board[row][j] = False 
+
+    # check top, left diagonal, right diagonal
+    def isValid(self,i,j,n):
+        r = i
+        c = j
+        while r >= 0:
+            if self.board[r][c]:
+                return False 
+            r-=1
+        r = i
+        c = j
+        while r >= 0 and c >= 0:
+            if self.board[r][c]:
+                return False 
+            r-=1
+            c-=1
+        r = i
+        c = j
+        while r >= 0 and c < n:
+            if self.board[r][c]:
+                return False 
+            r-=1
+            c+=1
+        return True
+
+    def solveNQueens(self, n: int) -> List[List[str]]:
+        self.final_arr = []
+        self.board = [[False]*n for _ in range(n)]
+        self.helper(0,n)
+        return self.final_arr

problem2.py

@@ -0,0 +1,33 @@
+# problem 2 
+
+#https://leetcode.com/problems/word-search/
+
+class Solution:
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        self.m = len(board)
+        self.n = len(board[0])
+        self.word = word
+        for i in range(self.m):
+            for j in range(self.n):
+                if self.helper(board,i,j,0):
+                    return True
+        return False
+
+
+
+    def helper(self,board,i,j,idx):
+        if idx == len(self.word):
+            return True 
+        if i<0 or j <0 or i>=self.m or j>=self.n or board[i][j] == '#':
+            return False 
+        if self.word[idx] != board[i][j]:
+            return False
+        dirs = [[-1,0],[0,-1],[1,0],[0,1]]
+        board[i][j] = '#'
+        for dir_s in dirs:
+            r = dir_s[0] + i
+            c = dir_s[1] + j
+            if self.helper(board,r,c,idx+1):
+                return True
+        board[i][j] = self.word[idx]
+        return False