Merge branch 'TheAlgorithms:master' into master

suryapratapsinghsuryavanshi · web-flow · commit 95bc95401dc8 · 2021-08-23T10:35:46.000+05:30
diff --git a/Backtracking/RatInAMaze.js b/Backtracking/RatInAMaze.js
@@ -0,0 +1,67 @@
+/*
+ * Problem Statement:
+ * - 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
+  }
+}
+
+const printPath = (grid, currentRow, currentColumn, path) => {
+  // If cell is out of boundary, we can't proceed
+  if (outOfBoundary(grid, currentRow, currentColumn)) return false
+
+  // If cell is blocked then you can't go ahead
+  if (grid[currentRow][currentColumn] === 0) return false
+
+  // If we reached target cell, then print path
+  if (currentRow === targetRow && currentColumn === targetColumn) {
+    console.log(path)
+    return true
+  }
+
+  // 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]
+    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, 1],
+  [1, 1, 0, 1]
+]
+
+const targetRow = grid.length - 1
+const targetColumn = grid[0].length - 1
+
+// 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')
diff --git a/DIRECTORY.md b/DIRECTORY.md
@@ -5,6 +5,7 @@
   * [GeneratePermutations](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/GeneratePermutations.js)
   * [KnightTour](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/KnightTour.js)
   * [NQueen](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/NQueen.js)
+  * [RatInAMaze](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/RatInAMaze.js)
   * [Sudoku](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/Sudoku.js)
   * tests
     * [NQueen](https://github.com/TheAlgorithms/Javascript/blob/master/Backtracking/tests/NQueen.test.js)
