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[mypy] Add/fix type annotations for backtracking algorithms (#4055)

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* Fix mypy errors for backtracking algorithms

* Fix CI failure
This commit is contained in:
Dhruv Manilawala
2020-12-24 18:16:21 +05:30
committed by GitHub
parent 0ccb213c11
commit f3ba9b6c50
7 changed files with 101 additions and 109 deletions
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63
backtracking/n_queens_math.py
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@ -75,14 +75,14 @@ Applying this two formulas we can check if a queen in some position is being att
for another one or vice versa.
"""
from __future__ import annotations
from typing import List
def depth_first_search(
possible_board: list[int],
diagonal_right_collisions: list[int],
diagonal_left_collisions: list[int],
boards: list[list[str]],
possible_board: List[int],
diagonal_right_collisions: List[int],
diagonal_left_collisions: List[int],
boards: List[List[str]],
n: int,
) -> None:
"""
@ -94,40 +94,33 @@ def depth_first_search(
['. . Q . ', 'Q . . . ', '. . . Q ', '. Q . . ']
"""
""" Get next row in the current board (possible_board) to fill it with a queen """
# Get next row in the current board (possible_board) to fill it with a queen
row = len(possible_board)
"""
If row is equal to the size of the board it means there are a queen in each row in
the current board (possible_board)
"""
# If row is equal to the size of the board it means there are a queen in each row in
# the current board (possible_board)
if row == n:
"""
We convert the variable possible_board that looks like this: [1, 3, 0, 2] to
this: ['. Q . . ', '. . . Q ', 'Q . . . ', '. . Q . ']
"""
possible_board = [". " * i + "Q " + ". " * (n - 1 - i) for i in possible_board]
boards.append(possible_board)
# We convert the variable possible_board that looks like this: [1, 3, 0, 2] to
# this: ['. Q . . ', '. . . Q ', 'Q . . . ', '. . Q . ']
boards.append([". " * i + "Q " + ". " * (n - 1 - i) for i in possible_board])
return
""" We iterate each column in the row to find all possible results in each row """
# We iterate each column in the row to find all possible results in each row
for col in range(n):
"""
We apply that we learned previously. First we check that in the current board
(possible_board) there are not other same value because if there is it means
that there are a collision in vertical. Then we apply the two formulas we
learned before:
45º: y - x = b or 45: row - col = b
135º: y + x = b or row + col = b.
And we verify if the results of this two formulas not exist in their variables
respectively. (diagonal_right_collisions, diagonal_left_collisions)
If any or these are True it means there is a collision so we continue to the
next value in the for loop.
"""
# We apply that we learned previously. First we check that in the current board
# (possible_board) there are not other same value because if there is it means
# that there are a collision in vertical. Then we apply the two formulas we
# learned before:
#
# 45º: y - x = b or 45: row - col = b
# 135º: y + x = b or row + col = b.
#
# And we verify if the results of this two formulas not exist in their variables
# respectively. (diagonal_right_collisions, diagonal_left_collisions)
#
# If any or these are True it means there is a collision so we continue to the
# next value in the for loop.
if (
col in possible_board
or row - col in diagonal_right_collisions
@ -135,7 +128,7 @@ def depth_first_search(
):
continue
""" If it is False we call dfs function again and we update the inputs """
# If it is False we call dfs function again and we update the inputs
depth_first_search(
possible_board + [col],
diagonal_right_collisions + [row - col],
@ -146,10 +139,10 @@ def depth_first_search(
def n_queens_solution(n: int) -> None:
boards = []
boards: List[List[str]] = []
depth_first_search([], [], [], boards, n)
""" Print all the boards """
# Print all the boards
for board in boards:
for column in board:
print(column)