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n-queens.py
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n-queens.py
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import timeit
def backtrackSolveNQueens(n: int):
def isValid(board, row: int, col: int) -> bool:
for i in range(col):
if board[row][i] == 1:
return False
i, j = row, col
while i >= 0 and j >= 0:
if board[i][j] == 1:
return False
i, j = i-1, j-1
i, j = row, col
while i < n and j >= 0:
if board[i][j] == 1:
return False
i, j = i+1, j-1
return True
def recoverSol(board):
res = []
for row in board:
s = ""
for col in row:
if col == 1:
s += "Q"
elif col == 0:
s += "."
res.append(s)
return res
solutions = []
def solve(board, col: int) -> bool:
if (col >= n):
solutions.append(recoverSol(board))
return False
for i in range(n):
if isValid(board, i, col):
board[i][col] = 1
solve(board, col+1)
board[i][col] = 0
return False
grid = [[0]*n for _ in range(n)]
solve(grid, 0)
return solutions
#print(backtrackSolveNQueens(16))
def wrapper():
return backtrackSolveNQueens(10)
print(len(wrapper()))
print(timeit.timeit(wrapper, number=1))