Rows of the Number Pyramid

Easy

The number pyramid (also known as Pascal's triangle) is built like this: the top row is a single 1; each next row is one number longer, has 1 at both ends, and every inner number equals the sum of the two numbers just above it to the left and to the right. Given rows, return the first rows rows of the pyramid from the top down, as a list of lists.

Example 1

rows=4 → [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]]

The third row is [1, 2, 1]; below it come 1, 1 + 2 = 3, 2 + 1 = 3, 1.

Example 2

rows=2 → [[1], [1, 1]]

Constraints

1 ≤ rows ≤ 30

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Topics

Array Dynamic Programming

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Input

rows=4

Expected

[[1], [1, 1], [1, 2, 1], [1, 3, 3, 1]]

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