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Author: shatakshigarg

BACKTRACKING/RAT IN A MAZE ALL PATHS.txt

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+/*
+	Note:
+	To get all the test cases accepted, make recursive calls in following order: Top, Down, Left, Right.
+	This means that if the current cell is (x, y), then order of calls should be: top cell (x-1, y), 
+	down cell (x+1, y), left cell (x, y-1) and right cell (x, y+1).
+*/  
+
+public class Solution {
+
+
+	static void ratInAMaze(int maze[][], int n) {
+		/* 
+			* Your class should be named Solution.
+			* Write your code here
+		 */
+        // n = maze.length;
+		int path[][]=new int[n][n];
+		printAllPaths(maze,0,0,path);
+	}
+	
+	public static void printAllPaths(int maze[][],int i,int j, int path[][])
+	{
+		int n = path.length;
+		if(i<0 || i>=n || j<0 || j>=n || maze[i][j]==0 || path[i][j]==1)
+		{
+			return;
+		}
+		path[i][j]=1;
+		
+		if(i==n-1 && j==n-1)
+		{
+			for(int r = 0;r<n;r++)
+			{
+				for(int c = 0;c<n;c++)
+				{
+					System.out.print(path[r][c]+" ");
+				}
+				// System.out.println();
+			}
+			System.out.println();
+			path[i][j]=0;
+			return;
+		}
+		
+		//top
+		printAllPaths(maze,i-1,j,path);
+		//down
+		printAllPaths(maze, i+1, j, path);
+		//right
+		printAllPaths(maze,i,j+1,path);
+		//left
+		printAllPaths(maze, i, j-1, path);
+		path[i][j]=0;
+		
+		
+		
+	}
+	
+	
+
+// 	public static void main(String[] args) {
+// 		int maze[][]= {{1,1,0},{1,1,0},{1,1,1}};
+// 		 ratInAMaze(maze,3);
+
+// 	}
+
+}

BACKTRACKING/RAT IN A MAZE.txt

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+
+public class Solution {
+
+	public static boolean ratInAMaze(int maze[][]){
+
+		/*Your class should be named Solution. 
+		*Don't write main().
+	 	*Don't take input, it is passed as function argument.
+	 	*Don't print output.
+	 	*Taking input and printing output is handled automatically.
+		*/ 
+    
+		int n = maze.length;	//row length
+		int path[][]= new int[n][n];
+		return solveMaze(maze, 0, 0, path);
+	}
+
+	public static boolean solveMaze(int maze[][],int i,int j, int path[][])
+	{
+		int n = maze.length;
+		//checking if the cell is a valid cell or not 
+		if(i<0 || i>=n || j<0 || j>=n || maze[i][j]==0 || path[i][j]==1)
+		{
+			return false;
+		}
+		//include cell in current path
+		path[i][j]=1;
+
+		//destination cell
+		if(i==n-1 && j==n-1)
+		{
+			return true;
+		}
+
+		//explore in all directions
+		//top
+		if(solveMaze(maze, i-1, j, path))
+		{
+			return true;
+		}
+		//right
+		if(solveMaze(maze, i, j+1, path))
+		{
+			return true;
+		}
+		//down
+		if(solveMaze(maze, i+1, j, path))
+		{
+			return true;
+		}
+		//left
+		if(solveMaze(maze, i, j-1, path))
+		{
+			return true;
+		}
+		
+		return false;
+		
+
+	}
+
+	public static void main(String[] args) {
+		int maze[][]= {{1,1,0},{1,1,0},{1,1,1}};
+		boolean pathpossible = ratInAMaze(maze);
+		System.out.println("Path exists?: "+pathpossible);
+	}
+
+}