Pascal’s Triangle

The first row is [1]. Each later row starts and ends with 1. Every interior entry is the sum of the two entries immediately above it. Return the first rows rows, beginning with the single 1.

Implement pascals_triangle(rows).

Input

rows: How many rows to generate.

Output

Return a list of rows, starting at the top; each row is a list of integers.

Contraintes

0 ≤ rows ≤ 60. Every entry fits a signed 64-bit integer. Zero rows returns an empty list.

Exemples

Entrée :
rows = 4

Sortie attendue :
expected = [
    [1],
    [1, 1],
    [1, 2, 1],
    [1, 3, 3, 1]
]

Entrée :
long long rows = 4;

Sortie attendue :
std::vector<std::vector<long long>> expected = {
    {1},
    {1, 1},
    {1, 2, 1},
    {1, 3, 3, 1}
};

Entrée :
long rows = 4;

Sortie attendue :
long[][] expected = new long[][] {
    new long[] {1},
    new long[] {1, 1},
    new long[] {1, 2, 1},
    new long[] {1, 3, 3, 1}
};

Entrée :
rows = 0

Sortie attendue :
expected = []

Entrée :
long long rows = 0;

Sortie attendue :
std::vector<std::vector<long long>> expected = {};

Entrée :
long rows = 0;

Sortie attendue :
long[][] expected = new long[][] {};

Références

Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.

• Pascal's Triangle