119. Pascal's Triangle II -- Python

119. Pascal’s Triangle II

Given an index k, return the kth row of the Pascal’s triangle.

For example, given k = 3,

Return [1,3,3,1].

Note:

Could you optimize your algorithm to use only O(k) extra space?

参考: 118. Pascal’s Triangle ，代码稍加修改只输出目标行数就行了

代码：

class Solution:
def generate(self, numRows):
"""
:type numRows: int
:rtype: List[List[int]]
"""
out=[]
for i in range(numRows+1):
out.append([1]*(i+1))
if i >1:
for j in range(1,i):
out[i][j]=out[i-1][j-1]+out[i-1][j]

return out[numRows][:]

更简洁的参考代码：

class Solution:
def getRow(self, rowIndex):
"""
:type rowIndex: int
:rtype: List[int]
"""
res = [1]
for i in range(rowIndex):
res = list(map(lambda x, y: x + y, [0] + res, res + [0]))
return res

其中用到了 map 和 lambda（快速实现函数）。