1 """
2 Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.
3 In Pascal's triangle, each number is the sum of the two numbers directly above it.
4 Example:
5 Input: 5
6 Output:
7 [
8 [1],
9 [1,1],
10 [1,2,1],
11 [1,3,3,1],
12 [1,4,6,4,1]
13 ]
14 """
15 """
16 解法一：
17 先来一个自己写的AC
18 直来直去，将第一行第二行单独拿出来讨论
19 第三行以后按照规律循环
20 """
21 class Solution1:
22 def generate(self, numRows):
23 if numRows <= 0:
24 return []
25 if numRows == 1:
26 return [[1]]
27 res = [[1], [1, 1]]
28 if numRows == 2:
29 return res
30 queue = [1, 1]
31 while numRows - 2:
32 temp = [1]
33 for i in range(len(queue)-1):
34 temp.append(queue[i] + queue[i+1])
35 temp.append(1)
36 res.append(temp)
37 queue = temp
38 numRows -= 1
39 return res
40 """
41 解法二：用map函数(自己知道这个函数,但想不到可以用,这就是和大佬的差距)
42 新的一行前后各添0,再相加即为下一行
43 0 1 3 3 1
44 +1 3 3 1 0
45 =1 4 6 4 1
46 """
47 class Solution:
48 def generate(self, numRows: int) -> List[List[int]]:
49 if numRows == 0:
50 return []
51 res = [[1]]
52 for i in range(1, numRows):
53 res.append(list(map(lambda x, y: x+y, res[-1] + [0], [0] + res[-1])))
54 # map(function, list1, list2)
55 #res[-1]代表当前最后一行,前后添0
56 # 0 1 3 3 1
57 # +1 3 3 1 0
58 # =1 4 6 4 1
59 return res
60 # '+'与extend功能相同,合二为一 []+[]=[]
61 # append是再末尾添加新的对象 [].append([]) = [[]]
