dist-javascript-algorithms-and-data-structures/dist/algorithms/uncategorized/unique-paths/btUniquePaths.js

Algorithms and data-structures implemented on JavaScript

"use strict";

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

/**
 * BACKTRACKING approach of solving Unique Paths problem.
 *
 * @param {number} width - Width of the board.
 * @param {number} height - Height of the board.
 * @param {number[][]} steps - The steps that have been already made.
 * @param {number} uniqueSteps - Total number of unique steps.
 * @return {number} - Number of unique paths.
 */
function btUniquePaths(width, height, steps = [[0, 0]], uniqueSteps = 0) {
  // Fetch current position on board.
  const currentPos = steps[steps.length - 1]; // Check if we've reached the end.

  if (currentPos[0] === width - 1 && currentPos[1] === height - 1) {
    // In case if we've reached the end let's increase total
    // number of unique steps.
    return uniqueSteps + 1;
  } // Let's calculate how many unique path we will have
  // by going right and by going down.


  let rightUniqueSteps = 0;
  let downUniqueSteps = 0; // Do right step if possible.

  if (currentPos[0] < width - 1) {
    steps.push([currentPos[0] + 1, currentPos[1]]); // Calculate how many unique paths we'll get by moving right.

    rightUniqueSteps = btUniquePaths(width, height, steps, uniqueSteps); // BACKTRACK and try another move.

    steps.pop();
  } // Do down step if possible.


  if (currentPos[1] < height - 1) {
    steps.push([currentPos[0], currentPos[1] + 1]); // Calculate how many unique paths we'll get by moving down.

    downUniqueSteps = btUniquePaths(width, height, steps, uniqueSteps); // BACKTRACK and try another move.

    steps.pop();
  } // Total amount of unique steps will be equal to total amount of
  // unique steps by going right plus total amount of unique steps
  // by going down.


  return rightUniqueSteps + downUniqueSteps;
}