JavaScript/Dynamic-Programming/UniquePaths2.js at master · TheAlgorithms/JavaScript · GitHub

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* Unique Paths 2

* There is a robot on an `m x n` grid.

* The robot is initially located at the top-left corner

* The robot tries to move to the bottom-right corner.

* The robot can only move either down or right at any point in time.

* Given grid with obstacles

* An obstacle and space are marked as 1 or 0 respectively in grid.

* A path that the robot takes cannot include any square that is an obstacle.

* Return the number of possible unique paths that the robot can take to reach the bottom-right corner.

* More info: https://leetcode.com/problems/unique-paths-ii/

/**

* @description Return 'rows x columns' grid with cells filled by 'filler'

* @param {Number} rows Number of rows in the grid

* @param {Number} columns Number of columns in the grid

* @param {String | Number | Boolean} filler The value to fill cells

* @returns {Array [][]}

const generateMatrix = (rows, columns, filler = 0) => {

const matrix = []

for (let i = 0; i < rows; i++) {

const submatrix = []

for (let k = 0; k < columns; k++) {

submatrix[k] = filler

}

matrix[i] = submatrix

}

return matrix

}

/**

* @description Return number of unique paths

* @param {Array [][]} obstacles Obstacles grid

* @returns {Number}

const uniquePaths2 = (obstacles) => {

if (!Array.isArray(obstacles)) {

throw new Error('Input data must be type of Array')

}

// Create grid for calculating number of unique ways

const rows = obstacles.length

const columns = obstacles[0].length

const grid = generateMatrix(rows, columns)

// Fill the outermost cell with 1 b/c it has

// the only way to reach neighbor

for (let i = 0; i < rows; i++) {

// If robot encounters an obstacle in these cells,

// he cannot continue moving in that direction

if (obstacles[i][0]) {

break

}

grid[i][0] = 1

}

for (let j = 0; j < columns; j++) {

if (obstacles[0][j]) {

break

}

grid[0][j] = 1

}

// Fill the rest of grid by dynamic programming

// using following recurrent formula:

// K[i][j] = K[i - 1][j] + K[i][j - 1]

for (let i = 1; i < rows; i++) {

for (let j = 1; j < columns; j++) {

grid[i][j] = obstacles[i][j] ? 0 : grid[i - 1][j] + grid[i][j - 1]

}

return grid[rows - 1][columns - 1]

}

export { uniquePaths2 }

JavaScript/Dynamic-Programming/UniquePaths2.js at master · TheAlgorithms/JavaScript · GitHub

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JavaScript/Dynamic-Programming/UniquePaths2.js at master · TheAlgorithms/JavaScript · GitHub

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