Searching for the subsequent location in a 2D array relative to the current position

Question

Searching for the subsequent location in a 2D array relative to the current position

Let's imagine we have a 3x4 array:

const arr = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]

. If we provide the input as

["straight", "right", "left"]

, the starting position being arr[0][0] and initial direction as "east".

[
 [1,  2,  3,  4],
 [5,  6,  7,  8],
 [9, 10, 11, 12]
]

Starting from the initial position moving "straight" would result in 2. Next, taking a "right" turn should lead to 6, followed by making a "left" turn resulting in 7.

What is the JavaScript algorithm needed to achieve this?

javascript arrays multidimensional-array

Answer 1

Answer №1

Develop a mapping system that determines the next direction based on the current direction and movement.
For each movement, compute the subsequent direction, verify if it is valid, and then provide the following value, position, and direction. Continue this process for every move.
If an invalid move occurs at any point, an error will be thrown. You have the option to tailor the error handling to suit your requirements.

const nextDirMap = {
  north: { left: "west", right: "east", straight: "north" },
  south: { left: "east", right: "west", straight: "south" },
  east: { left: "north", right: "south", straight: "east" },
  west: { left: "south", right: "north", straight: "west" },
};

function getNextPos(grid, currPos, currDir, move) {
  const nextDir = nextDirMap[currDir][move];
  const [r, c] = currPos;
  const maxRowLength = grid.length;
  const maxColLength = grid[0].length;

  switch (nextDir) {
    case "north": {
      if (r <= 0) {
        throw "Unable to move";
      }
      return { val: grid[r - 1][c], pos: [r - 1, c], dir: "north" };
    }
    case "south": {
      if (r >= maxRowLength) {
        throw "Unable to move";
      }
      return { val: grid[r + 1][c], pos: [r + 1, c], dir: "south" };
    }
    case "east": {
      if (c >= maxColLength) {
        throw "Unable to move";
      }
      return { val: grid[r][c + 1], pos: [r, c + 1], dir: "east" };
    }
    case "west": {
      if (c <= 0) {
        throw "Unable to move";
      }
      return { val: grid[r][c - 1], pos: [r, c - 1], dir: "west" };
    }
  }
}

function solution(grid, initPos, initDir, moves) {
  let currPos = initPos;
  let currDir = initDir;
  let currVal;
  moves.forEach((move) => {
    let { val, pos, dir } = getNextPos(grid, currPos, currDir, move);
    currDir = dir;
    currPos = pos;
    currVal = val;
  });
  return currVal;
}

const res = solution(
  [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12],
  ],
  [0, 0],
  "east",
  ["straight", "right", "left"]
);

console.log(res); // 7

It should be noted that this solution presupposes the existence of a valid grid with consistent column numbers across all rows, and there must be at least one row present.

Answer 2

Develop a mapping system that determines the next direction based on the current direction and movement.
For each movement, compute the subsequent direction, verify if it is valid, and then provide the following value, position, and direction. Continue this process for every move.
If an invalid move occurs at any point, an error will be thrown. You have the option to tailor the error handling to suit your requirements.

const nextDirMap = {
  north: { left: "west", right: "east", straight: "north" },
  south: { left: "east", right: "west", straight: "south" },
  east: { left: "north", right: "south", straight: "east" },
  west: { left: "south", right: "north", straight: "west" },
};

function getNextPos(grid, currPos, currDir, move) {
  const nextDir = nextDirMap[currDir][move];
  const [r, c] = currPos;
  const maxRowLength = grid.length;
  const maxColLength = grid[0].length;

  switch (nextDir) {
    case "north": {
      if (r <= 0) {
        throw "Unable to move";
      }
      return { val: grid[r - 1][c], pos: [r - 1, c], dir: "north" };
    }
    case "south": {
      if (r >= maxRowLength) {
        throw "Unable to move";
      }
      return { val: grid[r + 1][c], pos: [r + 1, c], dir: "south" };
    }
    case "east": {
      if (c >= maxColLength) {
        throw "Unable to move";
      }
      return { val: grid[r][c + 1], pos: [r, c + 1], dir: "east" };
    }
    case "west": {
      if (c <= 0) {
        throw "Unable to move";
      }
      return { val: grid[r][c - 1], pos: [r, c - 1], dir: "west" };
    }
  }
}

function solution(grid, initPos, initDir, moves) {
  let currPos = initPos;
  let currDir = initDir;
  let currVal;
  moves.forEach((move) => {
    let { val, pos, dir } = getNextPos(grid, currPos, currDir, move);
    currDir = dir;
    currPos = pos;
    currVal = val;
  });
  return currVal;
}

const res = solution(
  [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12],
  ],
  [0, 0],
  "east",
  ["straight", "right", "left"]
);

console.log(res); // 7

It should be noted that this solution presupposes the existence of a valid grid with consistent column numbers across all rows, and there must be at least one row present.

Searching for the subsequent location in a 2D array relative to the current position

Answer №1

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