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| 1 | +/* Java program to solve Rat in a Maze problem using backtracking */ |
| 2 | + |
| 3 | +public class RatMaze { |
| 4 | + |
| 5 | + // Size of the maze |
| 6 | + static int N; |
| 7 | + |
| 8 | + /* A utility function to print solution matrix sol[N][N] */ |
| 9 | + void printSolution(int sol[][]) |
| 10 | + { |
| 11 | + for (int i = 0; i < N; i++) { |
| 12 | + for (int j = 0; j < N; j++) |
| 13 | + System.out.print( |
| 14 | + " " + sol[i][j] + " "); |
| 15 | + System.out.println(); |
| 16 | + } |
| 17 | + } |
| 18 | + |
| 19 | + /* A utility function to check if x, y is valid index for N*N maze */ |
| 20 | + boolean isSafe( |
| 21 | + int maze[][], int x, int y) |
| 22 | + { |
| 23 | + // if (x, y outside maze) return false |
| 24 | + return (x >= 0 && x < N && y >= 0 |
| 25 | + && y < N && maze[x][y] == 1); |
| 26 | + } |
| 27 | + |
| 28 | + /* This function solves the Maze problem using Backtracking. It mainly uses solveMazeUtil() to solve the problem. It returns false if no path is possible, otherwise return true and |
| 29 | + prints the path in the form of 1s. Please note that there may be more than one solutions, this function prints one of the feasible solutions.*/ |
| 30 | + boolean solveMaze(int maze[][]) |
| 31 | + { |
| 32 | + int sol[][] = new int[N][N]; |
| 33 | + |
| 34 | + if (solveMazeUtil(maze, 0, 0, sol) == false) { |
| 35 | + System.out.print("Solution doesn't exist"); |
| 36 | + return false; |
| 37 | + } |
| 38 | + |
| 39 | + printSolution(sol); |
| 40 | + return true; |
| 41 | + } |
| 42 | + |
| 43 | + /* A recursive utility function to solve Maze problem */ |
| 44 | + boolean solveMazeUtil(int maze[][], int x, int y, |
| 45 | + int sol[][]) |
| 46 | + { |
| 47 | + // if (x, y is goal) return true |
| 48 | + if (x == N - 1 && y == N - 1 |
| 49 | + && maze[x][y] == 1) { |
| 50 | + sol[x][y] = 1; |
| 51 | + return true; |
| 52 | + } |
| 53 | + |
| 54 | + // Check if maze[x][y] is valid |
| 55 | + if (isSafe(maze, x, y) == true) { |
| 56 | + // mark x, y as part of solution path |
| 57 | + sol[x][y] = 1; |
| 58 | + |
| 59 | + /* Move forward in x direction */ |
| 60 | + if (solveMazeUtil(maze, x + 1, y, sol)) |
| 61 | + return true; |
| 62 | + |
| 63 | + /* If moving in x direction doesn't give solution then Move down in y direction */ |
| 64 | + if (solveMazeUtil(maze, x, y + 1, sol)) |
| 65 | + return true; |
| 66 | + |
| 67 | + /* If none of the above movements works then BACKTRACK: unmark x, y as part of solution path */ |
| 68 | + sol[x][y] = 0; |
| 69 | + return false; |
| 70 | + } |
| 71 | + |
| 72 | + return false; |
| 73 | + } |
| 74 | + |
| 75 | + public static void main(String args[]) |
| 76 | + { |
| 77 | + RatMaze rat = new RatMaze(); |
| 78 | + int maze[][] = { { 1, 0, 0, 0 }, |
| 79 | + { 1, 1, 0, 1 }, |
| 80 | + { 0, 1, 0, 0 }, |
| 81 | + { 1, 1, 1, 1 } }; |
| 82 | + |
| 83 | + N = maze.length; |
| 84 | + rat.solveMaze(maze); |
| 85 | + } |
| 86 | +} |
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