Math Pascal's triangle and combinations
101. Pascal's Triangle II
Pascal's triangle is a triangle of numbers. Its top row is a single 1. Each row below has one more number than the row above it. It starts and ends with 1, and every number in between is the sum of the two numbers just above it.
The rows are counted from 0, so row 0 is [1], row 1 is [1,1] and row 2 is [1,2,1]. Given an
integer rowIndex, return row rowIndex of Pascal's triangle, as a list of its numbers from left to
right.
Example 1
Input: rowIndex = 7
[1,7,21,35,35,21,7,1]Explanation: Row 6 is 1, 6, 15, 20, 15, 6, 1. Each number between the ends of row 7 adds two neighbours from it: 7 = 1 + 6, 21 = 6 + 15 and 35 = 15 + 20.
Example 2
Input: rowIndex = 0
[1]Explanation: Rows are counted from 0, so row 0 is the single 1 at the top.
Example 3
Input: rowIndex = 40
[1,40,780,9880,91390,658008,3838380,18643560,76904685,273438880,847660528,2311801440,5586853480,12033222880,23206929840,40225345056,62852101650,88732378800,113380261800,131282408400,137846528820,131282408400,113380261800,88732378800,62852101650,40225345056,23206929840,12033222880,5586853480,2311801440,847660528,273438880,76904685,18643560,3838380,658008,91390,9880,780,40,1]Check your understanding
Work out the answer for this input before you write any code.
Constraints
0 ≤ rowIndex ≤ 66
Clarifying questions
What you would ask an interviewer before writing any code.