Pascal's Triangle II - Leetcode 119 - Python

[@m.kamalali]

We can do the follow up using only 1 array by updating the array backward
row=[1]
for i in range(rowIndex):
row.append(1)
for j in range(i,0,-1):
row[j]+=row[j-1]
return row

[@commonguy7]

fkin genious bro

[@VidyaBhandary]

A Q&A video and two problems .. you are on a roll. Thanks for making these videos !

[@YehorKozyr]

This solution works, but it doesn't cover the mathematical meaning of Pascal's triangle and therefore can be simplified into a time and space O(rowIndex) function with a calculation of binomial coefficients.

[@pbenikovszky1]

sure, and the cpu will easily handle rowindex 1000 :D

[@sickboydroid]

@@pbenikovszky1 there is a easier way to calculate binomial coefficients without calculating factorials. Here is js version:
function nCr(n, r) {
if(r === 0 || n === r) return 1;
if(r > n/2) r = n-r;
let res = 1;
for(let i = 1; i

[@rajanmaheshwari]

Just did this few hours back 😃

[@ashesh8085]

My approach to this problem was to try to figure out a function such that:
f(n, i) = ans[i] ;
Meaning there would be a function which when given the rowIndex would be able to calculate the value of i th element in the row. Does a function like this exist? Is it even possible? This to me would seem much more efficient.
Here are some examples of this functions:
f(5,5) = 1
f(4,2) = 6
f(5,2) = 10
f(5,3) = 10
f(n, 0) = 1
f(n, n) = 1 .... etc.
Update: This is the binomial coefficient function

[@Mercer80]

C++
class Solution {
public:
vector getRow(int rowIndex) {
vectorprev(rowIndex+1);
for(int r=0;r

[@krateskim4169]

Awesome solution

[@xaceffulgent]

Discovered this channel recently and am learning a lot! Thank you! Beginner question: why do you put your sol in a class?

[@chuckle_pugz96]

'cause leetcode is passing all the inputs to this class in the background. Though some sites just use a function.

[@anjalivas1111]

hi @NeetCodeIO code isn't working for current format of the question Leetcode 119. Code returns [1] always. Can you please check? Thank you

[@AustinWeeks]

my friend you have to figure it out on your own sometimes

[@infoknow3278]

Easiest to come up with
class Solution:
def getRow(self, rowIndex: int) -> List[int]:
res = [[1]]
for i in range(rowIndex):
tmp = [0] + res[-1] + [0]
row = []
for j in range(len(res[-1])+1):
row.append(tmp[j]+tmp[j+1])
res.append(row)
return res[rowIndex]

[@reqzonegaming7157]

Please Bro
Make video for
2905. Find Indices With Index and Value Difference II

[@MrBomb72]

There’s a good quality one here: th-cam.com/video/IL1PB8jnfhE/w-d-xo.htmlfeature=shared (found this from the top rated post under the solutions tab)

[@sickboydroid]

for math nerds:
----------------------------------------------------------------
TC: O(rowIndex)
SC: O(rowIndex)
----------------------------------------------------------------
var getRow = function(rowIndex) {
if(rowIndex === 0) return [1];
const row = new Array(rowIndex+1);
for(let i = 0; i n/2) r = n-r;
let res = 1;
for(let i = 1; i