Pascal's Triangle Leetcode Solution
In this tutorial, we are going to solve a leetcode Pascal's Triangle in python.
Task:
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
Solution:
from math import factorial
class Solution:
def generate(self, numRows: int) -> List[List[int]]:
lst, m = [], []
for i in range(numRows):
for j in range(i+1):
am = factorial(i) // (factorial(i-j) * factorial(j))
m.append(am)
lst.append(m)
m = []
return lst
Steps:
step1: First we will declare two empty lists that will return our answer.
step2: then we add 2 loops, first will loop over the numRows and another loop will run till (i+1) times. And inside the inner loop we apply some mathematics for calculating the value of variable am and appending it to the list m.
step3: Outside the inner loop but still inside the outer loop we append the m to our lst which is our required returned list for the solution.
step4: after appending on the lst, we again make the m empty in order to add new row values. And then we return the lst.
