119. Pascal's Triangle II

Description

Given an index k, return the k^th row of the Pascal's triangle.

For example, given k = 3, Return [1,3,3,1].

Note: Could you optimize your algorithm to use only O(k) extra space?

Solution

/**
 * @param {number} rowIndex
 * @return {number[]}
 */
var getRow = function(rowIndex) {
    "use strict";
    let row = [];
    for (let i = 0; i <= rowIndex; i++) {
        let ptr1 = i-1, ptr2 = i-2;
        for (let j = i; j >= 0; j--) {
            if (j === 0 || j === i) {
                row[j] = 1;
            } else {
                row[j] = row[ptr1]+row[ptr2];
                ptr1--;
                ptr2--;
            }
        }
    }
    return row;
};