|
1 | | -from collections import defaultdict |
2 | | -from math import comb |
3 | | -from typing import List |
4 | | - |
5 | | - |
6 | 1 | class Solution: |
7 | | - def waysToBuildRooms(self, prevRoom: List[int]) -> int: |
8 | | - modulo = 10**9 + 7 |
9 | | - ingoing = defaultdict(set) |
10 | | - outgoing = defaultdict(set) |
| 2 | + def waysToBuildRooms(self, prevRoom: List[int]) -> int: |
| 3 | + modulo = 10**9 + 7 |
| 4 | + ingoing = defaultdict(set) |
| 5 | + outgoing = defaultdict(set) |
11 | 6 |
|
12 | | - for i in range(1, len(prevRoom)): |
13 | | - ingoing[i].add(prevRoom[i]) |
14 | | - outgoing[prevRoom[i]].add(i) |
15 | | - ans = [1] |
| 7 | + for i in range(1, len(prevRoom)): |
| 8 | + ingoing[i].add(prevRoom[i]) |
| 9 | + outgoing[prevRoom[i]].add(i) |
| 10 | + ans = [1] |
16 | 11 |
|
17 | | - def recurse(i): |
18 | | - if len(outgoing[i]) == 0: |
19 | | - return1# just self |
| 12 | + def recurse(i): |
| 13 | + if len(outgoing[i]) == 0: |
| 14 | + return1 |
20 | 15 |
|
21 | | - nodes_in_tree = 0 |
22 | | - for v in outgoing[i]: |
23 | | - cn = recurse(v) |
24 | | - if nodes_in_tree != 0: |
25 | | - ans[0] *= comb(nodes_in_tree + cn, cn) |
26 | | - ans[0] %= modulo |
27 | | - nodes_in_tree += cn |
28 | | - return nodes_in_tree + 1 |
| 16 | + nodes_in_tree = 0 |
| 17 | + for v in outgoing[i]: |
| 18 | + cn = recurse(v) |
| 19 | + if nodes_in_tree != 0: |
| 20 | + ans[0] *= comb(nodes_in_tree + cn, cn) |
| 21 | + ans[0] %= modulo |
| 22 | + nodes_in_tree += cn |
| 23 | + return nodes_in_tree + 1 |
29 | 24 |
|
30 | | - recurse(0) |
31 | | - return ans[0] % modulo |
| 25 | + recurse(0) |
| 26 | + return ans[0] % modulo |
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