a-task.md

Задание

Описание

Матрицу можно представить в виде двумерного списка. Например, список [[1, 2, 3], [4, 5, 6], [7, 8, 9]] — это отображение матрицы:

1 2 3
4 5 6
7 8 9

Задача

Реализуйте и экспортируйте по умолчанию функцию buildSnailPath, которая принимает на вход матрицу и возвращает список элементов матрицы по порядку следования от левого верхнего элемента по часовой стрелке к внутреннему. Движение по матрице напоминает улитку.

Примеры

buildSnailPath([
  [1, 2],
  [3, 4],
]); // [1, 2, 4, 3]

buildSnailPath([
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9, 10, 11, 12],
]) // [1, 2, 3, 4, 8, 12, 11, 10, 9, 5, 6, 7] 

build-snail-path-dry.js

// eslint-disable-next-line no-unused-vars
import { cloneDeep } from 'lodash';

// BEGIN (write your solution here)
export default function buildSnailPath(rawRoads) {
  const roads = cloneDeep(rawRoads);

  function isStepPassed(steps, x, y) {
    for (let i = 0; i < steps.length; i += 1) {
      if (steps[i].x === x && steps[i].y === y) {
        return true;
      }
    }

    return false;
  }

  function addRoadToStep(rawSteps, road, x, y) {
    const steps = cloneDeep(rawSteps);
    steps.push({
      x,
      y,
      road,
    });
    return steps;
  }

  function canGoTo(steps, x, y) {
    if (roads[x] && y >= 0 && y < roads[x].length) {
      return isStepPassed(steps, x, y) ? false : true;
    } else {
      return false;
    }
  }

  function computeXByDirection(value, direction) {
    return value + ({
      up: -1,
      right: 0,
      down: 1,
      left: 0,
    })[direction];
  }

  function computeYByDirection(value, direction) {
    return value + ({
      up: 0,
      right: 1,
      down: 0,
      left: -1,
    })[direction];
  }

  function changeDirectionСlockwise(direction) {
    return ({
      up: 'right',
      right: 'down',
      down: 'left',
      left: 'up',
    })[direction];
  }

  function goTo(rawSteps, x, y, direction) {
    const steps = canGoTo(rawSteps, x, y) ? addRoadToStep(rawSteps, roads[x][y], x, y) : cloneDeep(rawSteps);

    if (canGoTo(steps, computeXByDirection(x, direction), computeYByDirection(y, direction))) {
      return goTo(steps, computeXByDirection(x, direction), computeYByDirection(y, direction), direction);
    } else if (canGoTo(steps, computeXByDirection(x, changeDirectionСlockwise(direction)), computeYByDirection(y, changeDirectionСlockwise(direction)))) {
      return goTo(steps, computeXByDirection(x, changeDirectionСlockwise(direction)), computeYByDirection(y, changeDirectionСlockwise(direction)), changeDirectionСlockwise(direction));
    } else {
      return steps;
    }
  }

  return goTo([], 0, 0, 'right').map(i=>i.road);
}
// END

build-snail-path.js

// eslint-disable-next-line no-unused-vars
import { cloneDeep } from 'lodash';

// BEGIN (write your solution here)
export default function buildSnailPath(rawRoads) {
  const roads = cloneDeep(rawRoads);

  function isStepPassed(steps, x, y) {
    for (let i = 0; i < steps.length; i += 1) {
      if (steps[i].x === x && steps[i].y === y) {
        return true;
      }
    }

    return false;
  }

  function addRoadToStep(rawSteps, road, x, y) {
    const steps = cloneDeep(rawSteps);
    steps.push({
      x,
      y,
      road,
    });
    return steps;
  }

  function canGoTo(steps, x, y) {
    if (roads[x] && y >= 0 && y < roads[x].length) {
      return isStepPassed(steps, x, y) ? false : true;
    } else {
      return false;
    }
  }

  function goTo(rawSteps, x, y, direction) {
    const steps = canGoTo(rawSteps, x, y) ? addRoadToStep(rawSteps, roads[x][y], x, y) : cloneDeep(rawSteps);

    if (direction === 'up') {
      if (canGoTo(steps, x - 1, y)) {
        return goTo(steps, x - 1, y, 'up');
      } else if (canGoTo(steps, x, y + 1)) {
        return goTo(steps, x, y + 1, 'right');
      } else {
        return steps;
      }
    }

    if (direction === 'right') {
      if (canGoTo(steps, x, y + 1)) {
        return goTo(steps, x, y + 1, 'right');
      } else if (canGoTo(steps, x + 1, y)) {
        return goTo(steps, x + 1, y, 'down');
      } else {
        return steps;
      }
    }

    if (direction === 'down') {
      if (canGoTo(steps, x + 1, y)) {
        return goTo(steps, x + 1, y, 'down');
      } else if (canGoTo(steps, x, y - 1)) {
        return goTo(steps, x, y - 1, 'left');
      } else {
        return steps;
      }
    }

    if (direction === 'left') {
      if (canGoTo(steps, x, y - 1)) {
        return goTo(steps, x, y - 1, 'left');
      } else if (canGoTo(steps, x - 1, y)) {
        return goTo(steps, x - 1, y, 'up');
      } else {
        return steps;
      }
    }
  }

  return goTo([], 0, 0, 'right').map(i => i.road);
}
// END