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Add class documentation, improve comments in MazeRecursion.java (#5576)
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‎src/main/java/com/thealgorithms/backtracking/MazeRecursion.java

+89-116
Original file line numberDiff line numberDiff line change
@@ -1,152 +1,125 @@
11
package com.thealgorithms.backtracking;
22

3+
/**
4+
* This class contains methods to solve a maze using recursive backtracking.
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* The maze is represented as a 2D array where walls, paths, and visited/dead
6+
* ends are marked with different integers.
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*
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* The goal is to find a path from a starting position to the target position
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* (map[6][5]) while navigating through the maze.
10+
*/
311
public final class MazeRecursion {
12+
413
private MazeRecursion() {
514
}
615

7-
public static void mazeRecursion() {
8-
// First create a 2 dimensions array to mimic a maze map
9-
int[][] map = new int[8][7];
10-
int[][] map2 = new int[8][7];
11-
12-
// We use 1 to indicate wall
13-
// Set the ceiling and floor to 1
14-
for (int i = 0; i < 7; i++) {
15-
map[0][i] = 1;
16-
map[7][i] = 1;
17-
}
18-
19-
// Then we set the left and right wall to 1
20-
for (int i = 0; i < 8; i++) {
21-
map[i][0] = 1;
22-
map[i][6] = 1;
23-
}
24-
25-
// Now we have created a maze with its wall initialized
26-
27-
// Here we set the obstacle
28-
map[3][1] = 1;
29-
map[3][2] = 1;
30-
31-
// Print the current map
32-
System.out.println("The condition of the map： ");
33-
for (int i = 0; i < 8; i++) {
34-
for (int j = 0; j < 7; j++) {
35-
System.out.print(map[i][j] + " ");
36-
}
37-
System.out.println();
38-
}
39-
40-
// clone another map for setWay2 method
41-
for (int i = 0; i < map.length; i++) {
42-
System.arraycopy(map[i], 0, map2[i], 0, map[i].length);
43-
}
44-
45-
// By using recursive backtracking to let your ball(target) find its way in the
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// maze
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// The first parameter is the map
48-
// Second parameter is x coordinate of your target
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// Third parameter is the y coordinate of your target
50-
setWay(map, 1, 1);
51-
setWay2(map2, 1, 1);
52-
53-
// Print out the new map1, with the ball footprint
54-
System.out.println("After the ball goes through the map1，show the current map1 condition");
55-
for (int i = 0; i < 8; i++) {
56-
for (int j = 0; j < 7; j++) {
57-
System.out.print(map[i][j] + " ");
58-
}
59-
System.out.println();
16+
/**
17+
* This method solves the maze using the "down -> right -> up -> left"
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* movement strategy.
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*
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* @param map The 2D array representing the maze (walls, paths, etc.)
21+
* @return The solved maze with paths marked, or null if no solution exists.
22+
*/
23+
public static int[][] solveMazeUsingFirstStrategy(int[][] map) {
24+
if (setWay(map, 1, 1)) {
25+
return map;
6026
}
27+
return null;
28+
}
6129

62-
// Print out the new map2, with the ball footprint
63-
System.out.println("After the ball goes through the map2，show the current map2 condition");
64-
for (int i = 0; i < 8; i++) {
65-
for (int j = 0; j < 7; j++) {
66-
System.out.print(map2[i][j] + " ");
67-
}
68-
System.out.println();
30+
/**
31+
* This method solves the maze using the "up -> right -> down -> left"
32+
* movement strategy.
33+
*
34+
* @param map The 2D array representing the maze (walls, paths, etc.)
35+
* @return The solved maze with paths marked, or null if no solution exists.
36+
*/
37+
public static int[][] solveMazeUsingSecondStrategy(int[][] map) {
38+
if (setWay2(map, 1, 1)) {
39+
return map;
6940
}
41+
return null;
7042
}
7143

7244
/**
73-
* Using recursive path finding to help the ball find its way in the maze
74-
* Description：
75-
* 1. map (means the maze)
76-
* 2. i, j (means the initial coordinate of the ball in the maze)
77-
* 3. if the ball can reach the end of maze, that is position of map[6][5],
78-
* means the we have found a path for the ball
79-
* 4. Additional Information： 0 in the map[i][j] means the ball has not gone
80-
* through this position, 1 means the wall, 2 means the path is feasible, 3
81-
* means the ball has gone through the path but this path is dead end
82-
* 5. We will need strategy for the ball to pass through the maze for example:
83-
* Down -> Right -> Up -> Left, if the path doesn't work, then backtrack
45+
* Attempts to find a path through the maze using a "down -> right -> up -> left"
46+
* movement strategy. The path is marked with '2' for valid paths and '3' for dead ends.
8447
*
85-
* @author OngLipWei
86-
* @version Jun 23, 2021 11:36:14 AM
87-
* @param map The maze
88-
* @param i x coordinate of your ball(target)
89-
* @param j y coordinate of your ball(target)
90-
* @return If we did find a path for the ball，return true，else false
48+
* @param map The 2D array representing the maze (walls, paths, etc.)
49+
* @param i The current x-coordinate of the ball (row index)
50+
* @param j The current y-coordinate of the ball (column index)
51+
* @return True if a path is found to (6,5), otherwise false
9152
*/
92-
public static boolean setWay(int[][] map, int i, int j) {
93-
if (map[6][5] == 2) { // means the ball find its path, ending condition
53+
private static boolean setWay(int[][] map, int i, int j) {
54+
if (map[6][5] == 2) {
9455
return true;
9556
}
96-
if (map[i][j] == 0) { // if the ball haven't gone through this point
97-
// then the ball follows the move strategy : down -> right -> up -> left
98-
map[i][j] = 2; // we assume that this path is feasible first, set the current point to 2
99-
// first。
100-
if (setWay(map, i + 1, j)) { // go down
57+
58+
// If the current position is unvisited (0), explore it
59+
if (map[i][j] == 0) {
60+
// Mark the current position as '2'
61+
map[i][j] = 2;
62+
63+
// Move down
64+
if (setWay(map, i + 1, j)) {
10165
return true;
102-
} else if (setWay(map, i, j + 1)) { // go right
66+
}
67+
// Move right
68+
else if (setWay(map, i, j + 1)) {
10369
return true;
104-
} else if (setWay(map, i - 1, j)) { // go up
70+
}
71+
// Move up
72+
else if (setWay(map, i - 1, j)) {
10573
return true;
106-
} else if (setWay(map, i, j - 1)) { // go left
74+
}
75+
// Move left
76+
else if (setWay(map, i, j - 1)) {
10777
return true;
108-
} else {
109-
// means that the current point is the dead end, the ball cannot proceed, set
110-
// the current point to 3 and return false, the backtracking will start, it will
111-
// go to the previous step and check for feasible path again
112-
map[i][j] = 3;
113-
return false;
11478
}
115-
} else { // if the map[i][j] != 0 , it will probably be 1,2,3, return false because the
116-
// ball cannot hit the wall, cannot go to the path that has gone though before,
117-
// and cannot head to deadened.
79+
80+
map[i][j] = 3; // Mark as dead end (3) if no direction worked
11881
return false;
11982
}
83+
return false;
12084
}
12185

122-
// Here is another move strategy for the ball: up->right->down->left
123-
public static boolean setWay2(int[][] map, int i, int j) {
124-
if (map[6][5] == 2) { // means the ball find its path, ending condition
86+
/**
87+
* Attempts to find a path through the maze using an alternative movement
88+
* strategy "up -> right -> down -> left".
89+
*
90+
* @param map The 2D array representing the maze (walls, paths, etc.)
91+
* @param i The current x-coordinate of the ball (row index)
92+
* @param j The current y-coordinate of the ball (column index)
93+
* @return True if a path is found to (6,5), otherwise false
94+
*/
95+
private static boolean setWay2(int[][] map, int i, int j) {
96+
if (map[6][5] == 2) {
12597
return true;
12698
}
127-
if (map[i][j] == 0) { // if the ball haven't gone through this point
128-
// then the ball follows the move strategy : up->right->down->left
129-
map[i][j] = 2; // we assume that this path is feasible first, set the current point to 2
130-
// first。
131-
if (setWay2(map, i - 1, j)) { // go up
99+
100+
if (map[i][j] == 0) {
101+
map[i][j] = 2;
102+
103+
// Move up
104+
if (setWay2(map, i - 1, j)) {
132105
return true;
133-
} else if (setWay2(map, i, j + 1)) { // go right
106+
}
107+
// Move right
108+
else if (setWay2(map, i, j + 1)) {
134109
return true;
135-
} else if (setWay2(map, i + 1, j)) { // go down
110+
}
111+
// Move down
112+
else if (setWay2(map, i + 1, j)) {
136113
return true;
137-
} else if (setWay2(map, i, j - 1)) { // go left
114+
}
115+
// Move left
116+
else if (setWay2(map, i, j - 1)) {
138117
return true;
139-
} else {
140-
// means that the current point is the dead end, the ball cannot proceed, set
141-
// the current point to 3 and return false, the backtracking will start, it will
142-
// go to the previous step and check for feasible path again
143-
map[i][j] = 3;
144-
return false;
145118
}
146-
} else { // if the map[i][j] != 0 , it will probably be 1,2,3, return false because the
147-
// ball cannot hit the wall, cannot go to the path that has gone through before,
148-
// and cannot head to deadend.
119+
120+
map[i][j] = 3; // Mark as dead end (3) if no direction worked
149121
return false;
150122
}
123+
return false;
151124
}
152125
}

‎src/test/java/com/thealgorithms/backtracking/MazeRecursionTest.java

+14-20
Original file line numberDiff line numberDiff line change
@@ -11,41 +11,35 @@
1111
public class MazeRecursionTest {
1212

1313
@Test
14-
public void testMaze() {
15-
// First create a 2 dimensions array to mimic a maze map
14+
public void testSolveMazeUsingFirstAndSecondStrategy() {
1615
int[][] map = new int[8][7];
1716
int[][] map2 = new int[8][7];
1817

19-
// We use 1 to indicate wall
18+
// We use 1 to indicate walls
2019
// Set the ceiling and floor to 1
2120
for (int i = 0; i < 7; i++) {
2221
map[0][i] = 1;
2322
map[7][i] = 1;
2423
}
25-
26-
// Then we set the left and right wall to 1
24+
// Set the left and right wall to 1
2725
for (int i = 0; i < 8; i++) {
2826
map[i][0] = 1;
2927
map[i][6] = 1;
3028
}
31-
32-
// Now we have created a maze with its wall initialized
33-
34-
// Here we set the obstacle
29+
// Set obstacles
3530
map[3][1] = 1;
3631
map[3][2] = 1;
3732

38-
// clone another map for setWay2 method
33+
// Clone the original map for the second pathfinding strategy
3934
for (int i = 0; i < map.length; i++) {
40-
for (int j = 0; j < map[i].length; j++) {
41-
map2[i][j] = map[i][j];
42-
}
35+
System.arraycopy(map[i], 0, map2[i], 0, map[i].length);
4336
}
4437

45-
MazeRecursion.setWay(map, 1, 1);
46-
MazeRecursion.setWay2(map2, 1, 1);
47-
48-
int[][] expectedMap = new int[][] {
38+
// Solve the maze using the first strategy
39+
int[][] solvedMap1 = MazeRecursion.solveMazeUsingFirstStrategy(map);
40+
// Solve the maze using the second strategy
41+
int[][] solvedMap2 = MazeRecursion.solveMazeUsingSecondStrategy(map2);
42+
int[][] expectedMap1 = new int[][] {
4943
{1, 1, 1, 1, 1, 1, 1},
5044
{1, 2, 0, 0, 0, 0, 1},
5145
{1, 2, 2, 2, 0, 0, 1},
@@ -55,7 +49,6 @@ public void testMaze() {
5549
{1, 0, 0, 2, 2, 2, 1},
5650
{1, 1, 1, 1, 1, 1, 1},
5751
};
58-
5952
int[][] expectedMap2 = new int[][] {
6053
{1, 1, 1, 1, 1, 1, 1},
6154
{1, 2, 2, 2, 2, 2, 1},
@@ -67,7 +60,8 @@ public void testMaze() {
6760
{1, 1, 1, 1, 1, 1, 1},
6861
};
6962

70-
assertArrayEquals(map, expectedMap);
71-
assertArrayEquals(map2, expectedMap2);
63+
// Assert the results
64+
assertArrayEquals(expectedMap1, solvedMap1);
65+
assertArrayEquals(expectedMap2, solvedMap2);
7266
}
7367
}

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