Added NQueen and Rat in a maze solution in python

Backtracking/Code/SudokuSolver.py

@@ -0,0 +1,55 @@
+def check(grid, row, col, i):
+    for _ in range(9):
+        if grid[row][_] == i:
+            return False
+
+    for _ in range(9):
+        if grid[_][col] == i:
+            return False
+    ini_row = row - row % 3
+    ini_col = col - col % 3
+    for _ in range(3):
+        for k in range(3):
+            if grid[ini_row+_][ini_col+k] == i:
+                return False
+    return True
+
+
+def helper(grid, row, col):
+    if row == 9:
+        return True
+    if col == 9:
+        return helper(grid, row+1, 0)
+    if grid[row][col] != 0:
+        return helper(grid, row, col+1)
+
+    for _ in range(1, 10):
+        if check(grid, row, col, _):
+            grid[row][col] = _
+            if helper(grid, row, col+1):
+                return True
+        grid[row][col] = 0
+    return False
+
+
+def SolveSudoku(grid):
+    return helper(grid, 0, 0)
+
+
+def printGrid(grid):
+    SolveSudoku(grid)
+    for i in range(9):
+        for j in range(9):
+            print(grid[i][j], end=" ")
+
+
+grid = [[3, 0, 6, 5, 0, 8, 4, 0, 0],
+        [5, 2, 0, 0, 0, 0, 0, 0, 0],
+        [0, 8, 7, 0, 0, 0, 0, 3, 1],
+        [0, 0, 3, 0, 1, 0, 0, 8, 0],
+        [9, 0, 0, 8, 6, 3, 0, 0, 5],
+        [0, 5, 0, 0, 9, 0, 6, 0, 0],
+        [1, 3, 0, 0, 0, 0, 2, 5, 0],
+        [0, 0, 0, 0, 0, 0, 0, 7, 4],
+        [0, 0, 5, 2, 0, 6, 3, 0, 0]]
+printGrid(grid)

Backtracking/Code/nQueens.py

@@ -0,0 +1,49 @@
+ans = []
+
+
+def isSafe(board, i, j, n):
+    for u in range(n):
+        if board[u][j] == 1:
+            return False
+
+    for q, w in zip(range(i-1, -1, -1), range(j-1, -1, -1)):
+        if board[q][w] == 1:
+            return False
+    for q, w in zip(range(i-1, -1, -1), range(j+1, n, 1)):
+        if board[q][w] == 1:
+            return False
+    return True
+
+
+def helper(board, n, r):
+    if r == n:
+        temp = []
+        for k in range(n):
+            for l in range(n):
+                if board[k][l] == 1:
+                    temp.append(l+1)
+        ans.append(temp.copy())
+        return
+
+    for p in range(n):
+        if (isSafe(board, r, p, n)):
+            board[r][p] = 1
+            helper(board, n, r+1)
+            board[r][p] = 0
+
+
+def nQueen(n):
+
+    board = []
+    for _ in range(n):
+        my_list = []
+        for j in range(n):
+            my_list.append(0)
+        board.append(my_list)
+    # print(board)
+    helper(board, n, 0)
+    print(ans)
+
+
+    # helper(n)
+nQueen(3)

Backtracking/Code/ratInAMaze.py

@@ -0,0 +1,46 @@
+my_array = []
+
+
+def isSafe(input, visited, S_x, S_y, n):
+    if S_x >= 0 and S_y >= 0 and S_x < n and S_y < n and input[S_x][S_y] == 1 and visited[S_x][S_y] == 0:
+        return True
+    return False
+
+
+def helper(input, visited, n, S_x, S_y, temp):
+    if S_x == n-1 and S_y == n-1:
+        print(temp)
+        my_array.append(temp)
+        return
+    visited[S_x][S_y] = 1
+    if(isSafe(input, visited, S_x+1, S_y, n)):
+        helper(input, visited, n, S_x+1, S_y, temp + "D")
+    if(isSafe(input, visited, S_x, S_y-1, n)):
+        helper(input, visited, n, S_x, S_y-1, temp + "L")
+    if(isSafe(input, visited, S_x, S_y+1, n)):
+        helper(input, visited, n, S_x, S_y+1, temp + "R")
+    if(isSafe(input, visited, S_x-1, S_y, n)):
+        helper(input, visited, n, S_x-1, S_y, temp + "U")
+
+    visited[S_x][S_y] = 0
+    return
+
+
+def rat_in_a_maze(input, n):
+    visited = []
+    for _ in range(n):
+        my_list = []
+        for j in range(n):
+            my_list.append(0)
+        visited.append(my_list)
+    print(visited)
+    if input[0][0] == 0:
+        return
+    else:
+        helper(input, visited, n, 0, 0, "")
+
+
+input = [[1, 0, 0, 0], [1, 1, 0, 1], [1, 1, 0, 0], [0, 1, 1, 1]]
+
+rat_in_a_maze(input, len(input))
+print(my_array)