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No Plagiarism!RZcg1j6ont7GtKJRbRBSposted on PENANA Q: You have a 2-D grid of size m x n representing a box, and you have n balls. The box is open on the top and bottom sides.8964 copyright protection395PENANALoDm8hIfBW 維尼
Each cell in the box has a diagonal board spanning two corners of the cell that can redirect a ball to the right or to the left.8964 copyright protection395PENANA7pTx0kOgx0 維尼
- A board that redirects the ball to the right spans the top-left corner to the bottom-right corner and is represented in the grid as 1.
- A board that redirects the ball to the left spans the top-right corner to the bottom-left corner and is represented in the grid as -1.
We drop one ball at the top of each column of the box. Each ball can get stuck in the box or fall out of the bottom. A ball gets stuck if it hits a "V" shaped pattern between two boards or if a board redirects the ball into either wall of the box.8964 copyright protection395PENANASiUbPteKJJ 維尼
Return an array answer of size n where answer[i] is the column that the ball falls out of at the bottom after dropping the ball from the ith column at the top, or -1 if the ball gets stuck in the box.8964 copyright protection395PENANAfiFI05esvR 維尼
* [grid[0].length] = column number8964 copyright protection395PENANAzmCTLRoRHc 維尼
A: 8964 copyright protection395PENANAQIcHtbSDuZ 維尼
1. Depth First Search (DFS): 8964 copyright protection395PENANAVQuVfzA7AF 維尼
Condition 1: The ball reaches a point where it can no longer move ahead. In this case, we will return -1. Condition 2: The ball reaches the last row. In this case, we will return the column in which the ball will drop.8964 copyright protection395PENANAOGdrFPZ346 維尼
*Using Recursive function8964 copyright protection395PENANACpAKH8lYWU 維尼
class Solution {8964 copyright protection395PENANAitino8v6tT 維尼
public int[] findBall(int[][] grid) {8964 copyright protection395PENANAbYJARbooxm 維尼
// create new int[], for int[grid[0].length]8964 copyright protection395PENANAOOVmi5ty2C 維尼
int result[] = new int[grid[0].length];8964 copyright protection395PENANAWd52q5YYq6 維尼
// how many ball as well as how many row8964 copyright protection395PENANAqCU2KSs8LQ 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection395PENANAFJtLAySJ12 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection395PENANA54Sl6MJihZ 維尼
}8964 copyright protection395PENANA8ZJAadYDFy 維尼
return result;8964 copyright protection395PENANA5HdiK0leqe 維尼
}8964 copyright protection395PENANAgvbsD8vNsL 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection395PENANAmM2a9MNxrj 維尼
// base case; ball reached the last row8964 copyright protection395PENANAZarcYJARbx 維尼
if (row == grid.length)8964 copyright protection395PENANAIIozJKugsQ 維尼
return col;8964 copyright protection395PENANAT29KS9S3lc 維尼
int nextColumn = col + grid[row][col];8964 copyright protection395PENANAHsRKM0pcPL 維尼
if (nextColumn < 0 ||8964 copyright protection395PENANAFjMqjAI4Pr 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection395PENANAGtRDrwhKg4 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection395PENANAI9OM7rRilW 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection395PENANAzL7mPrYAUZ 維尼
return -1;8964 copyright protection395PENANA87psp1nvSo 維尼
}8964 copyright protection395PENANAWB7boewEUl 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection395PENANAlgaCVuos2T 維尼
}8964 copyright protection395PENANAHD2yjO1Uwy 維尼
}8964 copyright protection395PENANAWU12D6mtLF 維尼
2. Dynamic Programming Approach:8964 copyright protection395PENANAJwEcq8IOLY 維尼
class Solution {8964 copyright protection395PENANAcwof6E3GLx 維尼
public int[] findBall(int[][] grid) {8964 copyright protection395PENANAxma0hfw7y5 維尼
int result[] = new int[grid[0].length];8964 copyright protection395PENANAgItbisbmLV 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];399Please respect copyright.PENANAC3rknnZYgb
8964 copyright protection395PENANAi1byUiowwb 維尼
399Please respect copyright.PENANA39rsQ6Xgu1
8964 copyright protection395PENANAuqZSl2ktKp 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection395PENANAGExOWgqQRh 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection395PENANAX09Gl7CNb3 維尼
if (row == grid.length) {8964 copyright protection395PENANAYwCOHFTIsx 維尼
// for the last row 399Please respect copyright.PENANAgBf7qk9eAp
8964 copyright protection395PENANAP60OkTkrda 維尼
memo[row][col] = col;8964 copyright protection395PENANAsiiyOALO5A 維尼
continue;8964 copyright protection395PENANA3uphW1wVKM 維尼
}8964 copyright protection395PENANAElPX0wbbCE 維尼
// for the remaining row.8964 copyright protection395PENANAd1oq3wGlRt 維尼
int nextColumn = col + grid[row][col];8964 copyright protection395PENANAj5iuZd6sPZ 維尼
if (nextColumn < 0 ||8964 copyright protection395PENANAYQVDhloVPR 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection395PENANAz5dtMBpDFZ 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection395PENANAV8kPY3kfD1 維尼
memo[row][col] = -1;8964 copyright protection395PENANAan4QEuhQ2a 維尼
else8964 copyright protection395PENANAJKjUjlczAJ 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection395PENANAcGDaK8aU8Q 維尼
// reaching row 0, copy the values in all the column in the result array. 399Please respect copyright.PENANAnk5E2pkVgu
8964 copyright protection395PENANAlLoMKkFH1Z 維尼
if (row == 0) {8964 copyright protection395PENANATPQQAZCguA 維尼
result[col] = memo[row][col];8964 copyright protection395PENANArIl4TKjhaZ 維尼
}8964 copyright protection395PENANAkT7hai76VE 維尼
}8964 copyright protection395PENANAcqlgqJZB9B 維尼
}8964 copyright protection395PENANAVaMNTFDMVW 維尼
return result;8964 copyright protection395PENANAPlMqZXjnZk 維尼
}8964 copyright protection395PENANAEPCpBv4kBJ 維尼
}8964 copyright protection395PENANAHZvXv8uKcF 維尼
3. Iterative Approach, Simulation:8964 copyright protection395PENANAh5bwziNnEq 維尼
class Solution {8964 copyright protection395PENANAC3XXHFyxhc 維尼
public int[] findBall(int[][] grid) {8964 copyright protection395PENANADUiq0PB1Ta 維尼
int result[] = new int[grid[0].length];8964 copyright protection395PENANAYV43jfT6fW 維尼
// 1. Start by picking up a ball starting from every column col, iterating from the 0th column to the last column. Initialize the current column as col.8964 copyright protection395PENANAnmbvLa2siX 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection395PENANAv7hPIm3sv4 維尼
int currentCol = col;8964 copyright protection395PENANAFZqr8qVHQS 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection395PENANABq8aWcELKc 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection395PENANAXsUiko3kn7 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection395PENANAJ8pjETaGmA 維尼
// stuck case 8964 copyright protection395PENANAkBE3rX6jax 維尼
if (nextColumn < 0 ||8964 copyright protection395PENANAK2qLE9oIyd 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection395PENANAKSYgKULuUM 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection395PENANAYG6VxoPQpH 維尼
result[col] = -1;8964 copyright protection395PENANAx6WEQ7fWnE 維尼
break;8964 copyright protection395PENANAoxcFswFT68 維尼
}8964 copyright protection395PENANAt4FVgi0S82 維尼
// 3. Update the value of nextColumn in the result array for every row. In the end, the result will store the column number where the ball will fall after the last row. (result[col] = currentCol, return the result)8964 copyright protection395PENANAXmmZtq8TMB 維尼
result[col] = nextColumn;8964 copyright protection395PENANAEBi29lrxfb 維尼
currentCol = nextColumn;8964 copyright protection395PENANA3kmHiI97ZT 維尼
}8964 copyright protection395PENANAmjlfZLugLh 維尼
}8964 copyright protection395PENANAgjXi8U531C 維尼
return result;8964 copyright protection395PENANAFTHmPoHryS 維尼
}8964 copyright protection395PENANAL16gKKsgge 維尼
}8964 copyright protection395PENANAy7wjDAkMhC 維尼
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