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Pascal's Triangle II

Problem statement​

Given an integer rowIndex, return the rowIndexth (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 = 3Output: [1,3,3,1]

Example 2:

Input: rowIndex = 0Output: [1]

Example 3:

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

Constraints:

  • 0 <= rowIndex <= 33

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

My solution​

/**
 * @param {number} rowIndex
 * @return {number[]}
 */
var getRow = function(rowIndex) {
    if (rowIndex === 0) {
        return [1]
    }
    if (rowIndex === 1) {
        return [1, 1]
    }
    
    let count = 2;
    let answer = [1, 1]
    
    while (count <= rowIndex) {
        answer = [1, ...generate(answer), 1];
        count++
        // console.log("answer", answer)
    }
    
    return answer
};

function generate(arr) {
    const retArr = []
    for (let i = 0; i < arr.length - 1; i++) {
        // console.log(`${i} => ${arr[i]}:${arr[i + 1]}`)
        retArr.push(arr[i] + arr[i + 1])
    }
    
    // console.log(retArr)
    // console.log("----")
    return retArr
}