118. Pascal's Triangle

Given an integer numRows, return the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

 

Example 1:

Input: numRows = 5
Output: [[1],[1,1],[1,2,1],[1,3,3,1],[1,4,6,4,1]]

Example 2:

Input: numRows = 1
Output: [[1]]

 

Constraints:

• 1 <= numRows <= 30

---

class Solution:
    def generate(self, numRows: int) -> List[List[int]]:
        res=[[1]]
        for i in range(numRows-1):
            temp=[0] + res[-1] +[0]
            tlist=[]
            for j in range(len(res[-1])+1):
                tlist.append(temp[j]+temp[j+1])
            res.append(tlist)
        return res