PascalsTriangleIi.ts

// Source : https://leetcode.com/problems/pascals-triangle-ii/
// Author : squxq
// Date   : 2023-11-05

/*****************************************************************************************************
 *
 * 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?
 ******************************************************************************************************/

// number -> number[]
// produce all the elements in the given row, rowIndex, of a Pascal's triangle without computing other elements of factorials

// stub:
/**
function getRow(rowIndex: number): number[] {return [])
*/

// template:
/**
function getRow(rowIndex: number): number[] {
    return (... rowIndex)
}
*/

export function getRow(rowIndex: number): number[] {
  const row: number[] = new Array(rowIndex + 1);
  row[0] = 1;

  for (let k: number = 1; k <= rowIndex; k++) {
    row[k] = ((row[k - 1] as number) * (rowIndex + 1 - k)) / k;
  }

  return row;
}