Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.
class Solution(object):
def generate(self, numRows):
"""
:type numRows: int
:rtype: List[List[int]]
"""
ret = [[1],[1,1]]
row = [1,1]
if numRows==0:
ret = []
elif numRows==1:
ret = [[1]]
elif numRows==2:
ret = [[1],[1,1]]
else:
for i in range(2, numRows):
row = [1]+[row[x]+row[x-1] for x in range(1, i)]+[1]
ret.append(row)
return ret
1 一定要好好审题，比如这里numRows是说有多少row，并不是index
2 if分支在else的时候，和前面分支并没有联系，不能直接ret.append，需要重新初始化一个
