dist-javascript-algorithms-and-data-structures/dist/algorithms/uncategorized/jump-game/backtrackingJumpGame.js

Algorithms and data-structures implemented on JavaScript

"use strict";

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

/**
 * BACKTRACKING approach of solving Jump Game.
 *
 * This is the inefficient solution where we try every single jump
 * pattern that takes us from the first position to the last.
 * We start from the first position and jump to every index that
 * is reachable. We repeat the process until last index is reached.
 * When stuck, backtrack.
 *
 * @param {number[]} numbers - array of possible jump length.
 * @param {number} startIndex - index from where we start jumping.
 * @param {number[]} currentJumps - current jumps path.
 * @return {boolean}
 */
function backtrackingJumpGame(numbers, startIndex = 0, currentJumps = []) {
  if (startIndex === numbers.length - 1) {
    // We've jumped directly to last cell. This situation is a solution.
    return true;
  } // Check what the longest jump we could make from current position.
  // We don't need to jump beyond the array.


  const maxJumpLength = Math.min(numbers[startIndex], // Jump is within array.
  numbers.length - 1 - startIndex // Jump goes beyond array.
  ); // Let's start jumping from startIndex and see whether any
  // jump is successful and has reached the end of the array.

  for (let jumpLength = maxJumpLength; jumpLength > 0; jumpLength -= 1) {
    // Try next jump.
    const nextIndex = startIndex + jumpLength;
    currentJumps.push(nextIndex);
    const isJumpSuccessful = backtrackingJumpGame(numbers, nextIndex, currentJumps); // Check if current jump was successful.

    if (isJumpSuccessful) {
      return true;
    } // BACKTRACKING.
    // If previous jump wasn't successful then retreat and try the next one.


    currentJumps.pop();
  }

  return false;
}