119. Pascal's Triangle II

Problem

Tags: Array, Dynamic Programming

Given an integer rowIndex, return the rowIndex^th (0-indexed) row of the Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it as shown:

Example 1:

Input: rowIndex = 3
Output: [1,3,3,1]

Example 2:

Input: rowIndex = 0
Output: [1]

Example 3:

Input: rowIndex = 1
Output: [1,1]

Constraints:

• 0 <= rowIndex <= 33

Follow up: Could you optimize your algorithm to use only O(rowIndex) extra space?

Code

JS

// 119. Pascal's Triangle II (2/28/53841)
// Runtime: 72 ms (55.15%) Memory: 38.84 MB (94.95%) 

/**
 * @param {number} rowIndex
 * @return {number[]}
 */
function getRow(rowIndex) {
    const row = Array.from({ length: rowIndex + 1 });
    row[0] = 1;
    
    for(let i = 1; i <= rowIndex; i++) {
        row[i] = 1;
        for(let j = i - 1; j >= 1; j--) {
            row[j] += row[j - 1];
        }
    }
    
    return row;
};