diff --git a/Backtracking/RatInAMaze.js b/Backtracking/RatInAMaze.js index 923abcc5f..df38c4545 100644 --- a/Backtracking/RatInAMaze.js +++ b/Backtracking/RatInAMaze.js @@ -3,52 +3,65 @@ * - Given a NxN grid, find whether rat in cell (0,0) can reach target(N-1,N-1); * - In grid "0" represent blocked cell and "1" represent empty cell * + * Reference for this problem: + * - https://www.geeksforgeeks.org/rat-in-a-maze-backtracking-2/ + * */ +// Helper function to find if current cell is out of boundary const outOfBoundary = (grid, currentRow, currentColumn) => { - if (currentRow < 0 || currentColumn < 0 || currentRow >= grid.length || currentColumn >= grid[0].length) return true - else return false + if (currentRow < 0 || currentColumn < 0 || currentRow >= grid.length || currentColumn >= grid[0].length) { + return true + } else { + return false + } } -const isPossible = (grid, currentRow, currentColumn) => { - if (outOfBoundary(grid, currentRow, currentColumn)) return false +const printPath = (grid, currentRow, currentColumn, path) => { + // If cell is out of boundary, we can't proceed + if (outOfBoundary(grid, currentRow, currentColumn)) return false - if (grid[currentRow][currentColumn] === 0) return false + // If cell is blocked then you can't go ahead + if (grid[currentRow][currentColumn] === 0) return false - if (currentRow === targetRow && currentColumn === targetColumn) { - return true - } + // If we reached target cell, then print path + if (currentRow === targetRow && currentColumn === targetColumn) { + console.log(path) + return true + } - const directions = [ - [1, 0], - [0, 1], - [-1, 0], - [0, -1] - ] + // R,L,D,U are directions `Right, Left, Down, Up` + const directions = [ + [1, 0, 'D'], + [-1, 0, 'U'], + [0, 1, 'R'], + [0, -1, 'L'] + ] - for (let i = 0; i < directions.length; i++) { - const nextRow = currentRow + directions[i][0]; const nextColumn = currentColumn + directions[i][1] - grid[currentRow][currentColumn] = 0 - if (isPossible(grid, nextRow, nextColumn)) return true - grid[currentRow][currentColumn] = 1 - } - return false + for (let i = 0; i < directions.length; i++) { + const nextRow = currentRow + directions[i][0] + const nextColumn = currentColumn + directions[i][1] + const updatedPath = path + directions[i][2] + + grid[currentRow][currentColumn] = 0 + if (printPath(grid, nextRow, nextColumn, updatedPath)) return true + grid[currentRow][currentColumn] = 1 + } + return false } // Driver Code const grid = [ - [1, 1, 1, 1], - [1, 0, 0, 1], - [0, 0, 1, 0], - [1, 1, 0, 1] + [1, 1, 1, 1], + [1, 0, 0, 1], + [0, 0, 1, 1], + [1, 1, 0, 1] ] const targetRow = grid.length - 1 const targetColumn = grid[0].length - 1 -if (isPossible(grid, 0, 0)) { - console.log('Possible') -} else { - console.log('Not Possible') -} +// Variation 2 : print a possible path to reach from (0, 0) to (N-1, N-1) +// If there is no path possible then it will print "Not Possible" +!printPath(grid, 0, 0, '') && console.log('Not Possible')