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No Plagiarism!BEdcft0KbOZKVA7fOhP4posted 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 protection414PENANAt7Vvzt2Yfg 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 protection414PENANA27CLy0Ovja 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 protection414PENANAOrGAamf8Qj 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 protection414PENANAeW9H3u0qPJ 維尼
* [grid[0].length] = column number8964 copyright protection414PENANAxuImru1Dln 維尼
A: 8964 copyright protection414PENANA7dat59Q5hF 維尼
1. Depth First Search (DFS): 8964 copyright protection414PENANAdnaaOGzoJy 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 protection414PENANAxT445vGLky 維尼
*Using Recursive function8964 copyright protection414PENANAxU3cEIqSNN 維尼
class Solution {8964 copyright protection414PENANAa5AuiDtmwh 維尼
public int[] findBall(int[][] grid) {8964 copyright protection414PENANAJy3UXv57IO 維尼
// create new int[], for int[grid[0].length]8964 copyright protection414PENANA4O3dFXSat2 維尼
int result[] = new int[grid[0].length];8964 copyright protection414PENANAJc4IGosufB 維尼
// how many ball as well as how many row8964 copyright protection414PENANAa52Wi4Aw5x 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection414PENANA2WBucAcUQY 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection414PENANATEmVt36nXj 維尼
}8964 copyright protection414PENANAefO4JmAITq 維尼
return result;8964 copyright protection414PENANAYCagPKJasr 維尼
}8964 copyright protection414PENANAQiXUwncJZa 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection414PENANAQKjCyxjFOI 維尼
// base case; ball reached the last row8964 copyright protection414PENANAa6eNCJYzPI 維尼
if (row == grid.length)8964 copyright protection414PENANAFX8uQfdoey 維尼
return col;8964 copyright protection414PENANA3oZq8ylTeM 維尼
int nextColumn = col + grid[row][col];8964 copyright protection414PENANAqe31cLfdK5 維尼
if (nextColumn < 0 ||8964 copyright protection414PENANAYKNMoBm40u 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection414PENANASPWjFQv5Fw 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection414PENANAe0Rs6TdzK8 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection414PENANAwNVbmCwSc1 維尼
return -1;8964 copyright protection414PENANA29DAzv7R6Z 維尼
}8964 copyright protection414PENANAFROd7UuJ1Q 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection414PENANAXro01A3CLt 維尼
}8964 copyright protection414PENANAlFijy338Tl 維尼
}8964 copyright protection414PENANAxOUTFibjV6 維尼
2. Dynamic Programming Approach:8964 copyright protection414PENANARrsc02VPa8 維尼
class Solution {8964 copyright protection414PENANA2XGy4W2qax 維尼
public int[] findBall(int[][] grid) {8964 copyright protection414PENANAZriyIkcBtE 維尼
int result[] = new int[grid[0].length];8964 copyright protection414PENANAEHakPg6f1x 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];418Please respect copyright.PENANA0tZammB6pA
8964 copyright protection414PENANAsBXAGnjYr1 維尼
418Please respect copyright.PENANA7ljQsO2IG1
8964 copyright protection414PENANASh3O1Wonyv 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection414PENANAJ1qMxinJkc 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection414PENANAj8cntzcHE5 維尼
if (row == grid.length) {8964 copyright protection414PENANAhnS4XwOoFz 維尼
// for the last row 418Please respect copyright.PENANAYs2pZYFu4d
8964 copyright protection414PENANAJJYg1nD0Mt 維尼
memo[row][col] = col;8964 copyright protection414PENANATeoISsvAcB 維尼
continue;8964 copyright protection414PENANAS4lXIfnT14 維尼
}8964 copyright protection414PENANAB2SyTaVy8i 維尼
// for the remaining row.8964 copyright protection414PENANA0bf1tJ7pYd 維尼
int nextColumn = col + grid[row][col];8964 copyright protection414PENANApdWPUAuMjq 維尼
if (nextColumn < 0 ||8964 copyright protection414PENANAhssKvgdP94 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection414PENANA58CVS2W8QG 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection414PENANAj0pgB3XPi4 維尼
memo[row][col] = -1;8964 copyright protection414PENANAA8VvlaXnVD 維尼
else8964 copyright protection414PENANARJlyw9G26g 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection414PENANAF3GGbddgNz 維尼
// reaching row 0, copy the values in all the column in the result array. 418Please respect copyright.PENANAgqa6uXXUjh
8964 copyright protection414PENANALvaTUpK2oT 維尼
if (row == 0) {8964 copyright protection414PENANAWJHUH5s3Ko 維尼
result[col] = memo[row][col];8964 copyright protection414PENANA8ile4QjbU6 維尼
}8964 copyright protection414PENANA2b3Ffe0Y7Z 維尼
}8964 copyright protection414PENANAEdOtTLXrbc 維尼
}8964 copyright protection414PENANA9uqXZLeZcY 維尼
return result;8964 copyright protection414PENANAQEDYmev23O 維尼
}8964 copyright protection414PENANAWkBlKBQHuI 維尼
}8964 copyright protection414PENANApYJ262JcKZ 維尼
3. Iterative Approach, Simulation:8964 copyright protection414PENANAlBbtQo783z 維尼
class Solution {8964 copyright protection414PENANA64DFINfLq8 維尼
public int[] findBall(int[][] grid) {8964 copyright protection414PENANALeDm2egIHi 維尼
int result[] = new int[grid[0].length];8964 copyright protection414PENANAaVfItoSFty 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 protection414PENANAsQM0uUpPH1 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection414PENANADZNQVYFhdv 維尼
int currentCol = col;8964 copyright protection414PENANAMLuNLV7IVK 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection414PENANATrkRmHbEYL 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection414PENANAbKCDf1dwDk 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection414PENANAhESIs6R2xh 維尼
// stuck case 8964 copyright protection414PENANA1oWVTjgt8o 維尼
if (nextColumn < 0 ||8964 copyright protection414PENANAC6XGeTObI2 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection414PENANAoM5iFPaEqk 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection414PENANA0UWyxPfg24 維尼
result[col] = -1;8964 copyright protection414PENANAT3sPuZJ8fd 維尼
break;8964 copyright protection414PENANAhSTLVWKJBW 維尼
}8964 copyright protection414PENANA11INHO2FPO 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 protection414PENANAYeheiy4tBI 維尼
result[col] = nextColumn;8964 copyright protection414PENANAgkkD87mobf 維尼
currentCol = nextColumn;8964 copyright protection414PENANAhMgnLBESGq 維尼
}8964 copyright protection414PENANAQ2ktXs5LFN 維尼
}8964 copyright protection414PENANA4oGvYTn23D 維尼
return result;8964 copyright protection414PENANAxZv1VqeQoq 維尼
}8964 copyright protection414PENANAPApGzwM93H 維尼
}8964 copyright protection414PENANAMrM5QhxLst 維尼
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