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No Plagiarism!E9d517aJwGgAXwSSOrpFposted 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 protection398PENANAkJZz2PO7ta 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 protection398PENANA8aYWZWVFM1 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 protection398PENANAhbJwHFNQZV 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 protection398PENANAUINYdhXMsR 維尼
* [grid[0].length] = column number8964 copyright protection398PENANAujrjyFYOfG 維尼
A: 8964 copyright protection398PENANAepcD3He00N 維尼
1. Depth First Search (DFS): 8964 copyright protection398PENANANyyamiWYPV 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 protection398PENANAtraexsTtVj 維尼
*Using Recursive function8964 copyright protection398PENANAfo7E2pKyP5 維尼
class Solution {8964 copyright protection398PENANAHtN4Ktysvf 維尼
public int[] findBall(int[][] grid) {8964 copyright protection398PENANAxHmGsVz6t7 維尼
// create new int[], for int[grid[0].length]8964 copyright protection398PENANASyKhreZZXL 維尼
int result[] = new int[grid[0].length];8964 copyright protection398PENANA3pMeqjZIkX 維尼
// how many ball as well as how many row8964 copyright protection398PENANAt2KBJJgwxN 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection398PENANAw0YA6zVCLl 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection398PENANADkSGR4aVIi 維尼
}8964 copyright protection398PENANAjd3i4cq9pb 維尼
return result;8964 copyright protection398PENANAAEulkB5HtA 維尼
}8964 copyright protection398PENANAtKxa1Q5BBU 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection398PENANA7Me8ZP6Hgk 維尼
// base case; ball reached the last row8964 copyright protection398PENANAl8X8vNqJL5 維尼
if (row == grid.length)8964 copyright protection398PENANAifVPxhSwSZ 維尼
return col;8964 copyright protection398PENANAnuLiUbKQya 維尼
int nextColumn = col + grid[row][col];8964 copyright protection398PENANArgapiKQzUe 維尼
if (nextColumn < 0 ||8964 copyright protection398PENANAg9oig6cIUI 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection398PENANA1mGBn2p8EK 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection398PENANAszVftbFUpm 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection398PENANAOtsnYwczRA 維尼
return -1;8964 copyright protection398PENANAfrbtpxI8No 維尼
}8964 copyright protection398PENANAlXl8d1418Y 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection398PENANAHVM9JkxiRM 維尼
}8964 copyright protection398PENANAG9NFWRLX3x 維尼
}8964 copyright protection398PENANATxB5obyJeb 維尼
2. Dynamic Programming Approach:8964 copyright protection398PENANAsPRK904BZQ 維尼
class Solution {8964 copyright protection398PENANAubB9XOMurA 維尼
public int[] findBall(int[][] grid) {8964 copyright protection398PENANAzi4CvCAz7C 維尼
int result[] = new int[grid[0].length];8964 copyright protection398PENANANkDBIpV58n 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];402Please respect copyright.PENANARgWzmSGBXF
8964 copyright protection398PENANAK1itYmEvQG 維尼
402Please respect copyright.PENANAm75uBueZqu
8964 copyright protection398PENANAqscpZPawBW 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection398PENANAzAbczx2jZ6 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection398PENANAuN7kabS9SJ 維尼
if (row == grid.length) {8964 copyright protection398PENANAgDM9hLFpmQ 維尼
// for the last row 402Please respect copyright.PENANA98aEWS9HUl
8964 copyright protection398PENANAA6bKjnQZ5x 維尼
memo[row][col] = col;8964 copyright protection398PENANAcNa9z3Ccq6 維尼
continue;8964 copyright protection398PENANAfvK5zw1Wx5 維尼
}8964 copyright protection398PENANAHQ7TZemKnd 維尼
// for the remaining row.8964 copyright protection398PENANAKPXCBIbj7S 維尼
int nextColumn = col + grid[row][col];8964 copyright protection398PENANA4uuacQiNBc 維尼
if (nextColumn < 0 ||8964 copyright protection398PENANAdJYie9PHKC 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection398PENANAgVB0NPoqNX 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection398PENANAt60r268ao8 維尼
memo[row][col] = -1;8964 copyright protection398PENANAKzIvLa8tNY 維尼
else8964 copyright protection398PENANAC3ooizMRuY 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection398PENANAVWFXkZt7IV 維尼
// reaching row 0, copy the values in all the column in the result array. 402Please respect copyright.PENANA3BU9lxmuIt
8964 copyright protection398PENANArlS20U1eYe 維尼
if (row == 0) {8964 copyright protection398PENANAPzBD1Gg5xr 維尼
result[col] = memo[row][col];8964 copyright protection398PENANAaRJe0TVXns 維尼
}8964 copyright protection398PENANA5wGxU3fyE6 維尼
}8964 copyright protection398PENANA4OB6ifLbGK 維尼
}8964 copyright protection398PENANAYzUGywZuGW 維尼
return result;8964 copyright protection398PENANAGxb1ysEZuX 維尼
}8964 copyright protection398PENANAI3EeLPC5tp 維尼
}8964 copyright protection398PENANAnbkznlbgST 維尼
3. Iterative Approach, Simulation:8964 copyright protection398PENANASbDYfG7dUT 維尼
class Solution {8964 copyright protection398PENANAePn02QDfNB 維尼
public int[] findBall(int[][] grid) {8964 copyright protection398PENANAGGiwMFASCF 維尼
int result[] = new int[grid[0].length];8964 copyright protection398PENANAdFyOpYu2iV 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 protection398PENANAZkNJA3v1YZ 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection398PENANALMog8SvoB9 維尼
int currentCol = col;8964 copyright protection398PENANAeJes5mdpj3 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection398PENANAGQzc5d4EIJ 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection398PENANAkzVLaSqpno 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection398PENANASWpAogLGRk 維尼
// stuck case 8964 copyright protection398PENANAJtXn7pTYnD 維尼
if (nextColumn < 0 ||8964 copyright protection398PENANAjbGHYKrwjh 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection398PENANAqJeu2pVcso 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection398PENANAUdPqSXFCre 維尼
result[col] = -1;8964 copyright protection398PENANAgGLQeLtnQQ 維尼
break;8964 copyright protection398PENANAIXp30V7NZk 維尼
}8964 copyright protection398PENANA0mkLlpB04c 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 protection398PENANAU2wqrPy1QQ 維尼
result[col] = nextColumn;8964 copyright protection398PENANAGt3W1uJNEc 維尼
currentCol = nextColumn;8964 copyright protection398PENANAujvNGenQxR 維尼
}8964 copyright protection398PENANAVPV9pVuKkB 維尼
}8964 copyright protection398PENANA8Rkfv2oz43 維尼
return result;8964 copyright protection398PENANAjFY091mYRj 維尼
}8964 copyright protection398PENANAa2nzvDgbgp 維尼
}8964 copyright protection398PENANAcV8aGJxFTJ 維尼
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