dist-javascript-algorithms-and-data-structures/dist/algorithms/math/pascal-triangle/pascalTriangleRecursive.js

Algorithms and data-structures implemented on JavaScript

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = pascalTriangleRecursive;

/**
 * @param {number} lineNumber - zero based.
 * @return {number[]}
 */
function pascalTriangleRecursive(lineNumber) {
  if (lineNumber === 0) {
    return [1];
  }

  const currentLineSize = lineNumber + 1;
  const previousLineSize = currentLineSize - 1; // Create container for current line values.

  const currentLine = []; // We'll calculate current line based on previous one.

  const previousLine = pascalTriangleRecursive(lineNumber - 1); // Let's go through all elements of current line except the first and
  // last one (since they were and will be filled with 1's) and calculate
  // current coefficient based on previous line.

  for (let numIndex = 0; numIndex < currentLineSize; numIndex += 1) {
    const leftCoefficient = numIndex - 1 >= 0 ? previousLine[numIndex - 1] : 0;
    const rightCoefficient = numIndex < previousLineSize ? previousLine[numIndex] : 0;
    currentLine[numIndex] = leftCoefficient + rightCoefficient;
  }

  return currentLine;
}