-
Notifications
You must be signed in to change notification settings - Fork 5
/
n-queens.py
57 lines (50 loc) · 1.77 KB
/
n-queens.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
# @Title: N 皇后 (N-Queens)
# @Author: KivenC
# @Date: 2020-09-03 22:09:08
# @Runtime: 68 ms
# @Memory: 14 MB
class Solution:
# def solveNQueens(self, n: int) -> List[List[str]]:
# # 回溯
# # 利用三个集合记录皇后的位置
# self.col = set()
# self.diag_1 = set()
# self.diag_2 = set()
# self.res = []
# self.queens = [-1] * n
# self.row = ["."] * n
# self.backtrack(0, n)
# return self.res
# def generateGrid(self):
# grid = []
# for queen in self.queens:
# self.row[queen] = "Q"
# grid.append("".join(self.row))
# self.row[queen] = "."
# return grid
# def backtrack(self, i: int, n: int):
# if i == n:
# self.res.append(self.generateGrid())
# else:
# for j in range(n):
# if j in self.col or j - i in self.diag_1 or j + i in self.diag_2:
# continue
# self.queens[i] = j
# self.col.add(j)
# self.diag_1.add(j - i)
# self.diag_2.add(j + i)
# self.backtrack(i+1, n)
# self.col.remove(j)
# self.diag_1.remove(j - i)
# self.diag_2.remove(j + i)
def solveNQueens(self, n: int) -> List[List[str]]:
result = []
def helper(col, pie, na):
if len(col) == n:
result.append(col)
return
for i in range(n):
if i not in col and i-len(col) not in pie and i+len(col) not in na:
helper(col+[i], pie+[i-len(col)], na+[i+len(col)])
helper([], [], [])
return [['.' * i + 'Q' + '.' * (n-i-1) for i in r] for r in result]