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No Plagiarism!PNxAJLTN4YJytd7eYIK9posted 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 protection416PENANA6fwZ1ZH7ve 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 protection416PENANASImtvYhHBk 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 protection416PENANA0IwTW9Hv3P 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 protection416PENANAFRAxbqHXRP 維尼
* [grid[0].length] = column number8964 copyright protection416PENANAmu1M5OWdgn 維尼
A: 8964 copyright protection416PENANAfOxKXlkkGG 維尼
1. Depth First Search (DFS): 8964 copyright protection416PENANAc5KjlkNKFd 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 protection416PENANA7iyzsFurzF 維尼
*Using Recursive function8964 copyright protection416PENANASy7041kR8X 維尼
class Solution {8964 copyright protection416PENANAJMNOtlM97A 維尼
public int[] findBall(int[][] grid) {8964 copyright protection416PENANAB7NnWZ6R3I 維尼
// create new int[], for int[grid[0].length]8964 copyright protection416PENANABIibma81jG 維尼
int result[] = new int[grid[0].length];8964 copyright protection416PENANAzC1GDoDEOQ 維尼
// how many ball as well as how many row8964 copyright protection416PENANAnaBwYrUTBK 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection416PENANAApuMwZiuHC 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection416PENANALzfJM7W6OS 維尼
}8964 copyright protection416PENANAnUwC0a3Nos 維尼
return result;8964 copyright protection416PENANAPZz0Iake9R 維尼
}8964 copyright protection416PENANA2rzCVARRzX 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection416PENANAKHJadvbMfD 維尼
// base case; ball reached the last row8964 copyright protection416PENANAkGGPd1STiC 維尼
if (row == grid.length)8964 copyright protection416PENANAoMi7WsrBEu 維尼
return col;8964 copyright protection416PENANAA6vnOWazoB 維尼
int nextColumn = col + grid[row][col];8964 copyright protection416PENANAqPwKfS5Xoe 維尼
if (nextColumn < 0 ||8964 copyright protection416PENANAYTJNPyacom 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection416PENANAvlp3cGVji6 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection416PENANAUFiV5VmeZ5 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection416PENANAzoQrBKBqbZ 維尼
return -1;8964 copyright protection416PENANAl8DZIMLobz 維尼
}8964 copyright protection416PENANAVj1jrdbIG8 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection416PENANAL8sIcfcjsl 維尼
}8964 copyright protection416PENANAsy1293TU4d 維尼
}8964 copyright protection416PENANA3nw4YUYOix 維尼
2. Dynamic Programming Approach:8964 copyright protection416PENANAPct8OXexQB 維尼
class Solution {8964 copyright protection416PENANAWYFNZecgFh 維尼
public int[] findBall(int[][] grid) {8964 copyright protection416PENANAW6GYdmAVbq 維尼
int result[] = new int[grid[0].length];8964 copyright protection416PENANAuJkwCKsNkk 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];420Please respect copyright.PENANAwPmp5cIwBW
8964 copyright protection416PENANAGtVngFvM7r 維尼
420Please respect copyright.PENANAwRoyIclSy2
8964 copyright protection416PENANAAOQslz1qmb 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection416PENANApKxiISIfbg 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection416PENANA0NvLxk6F3D 維尼
if (row == grid.length) {8964 copyright protection416PENANAPGfNRnCAzq 維尼
// for the last row 420Please respect copyright.PENANA3av9ZYhn2V
8964 copyright protection416PENANAseV9t5vu1c 維尼
memo[row][col] = col;8964 copyright protection416PENANAc6linSdhHx 維尼
continue;8964 copyright protection416PENANAAqG7ZqdqYl 維尼
}8964 copyright protection416PENANAHuSdIzS9Y7 維尼
// for the remaining row.8964 copyright protection416PENANAF2hRE5bzII 維尼
int nextColumn = col + grid[row][col];8964 copyright protection416PENANAWpjeC5G81o 維尼
if (nextColumn < 0 ||8964 copyright protection416PENANAleHozCRVQJ 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection416PENANAfEa14oRryT 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection416PENANAfmPrEQPPIh 維尼
memo[row][col] = -1;8964 copyright protection416PENANASUJlcCyWZY 維尼
else8964 copyright protection416PENANAog1Tui7UPq 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection416PENANAd8NgGMTtoO 維尼
// reaching row 0, copy the values in all the column in the result array. 420Please respect copyright.PENANAUMpP0EnYQy
8964 copyright protection416PENANAINNPNDYDvT 維尼
if (row == 0) {8964 copyright protection416PENANAp7uHWTPde6 維尼
result[col] = memo[row][col];8964 copyright protection416PENANAOAAALybxFz 維尼
}8964 copyright protection416PENANAK4XN9ogAos 維尼
}8964 copyright protection416PENANAWTFRXDPEFi 維尼
}8964 copyright protection416PENANAsmkkTKApb6 維尼
return result;8964 copyright protection416PENANA122xnZFes4 維尼
}8964 copyright protection416PENANAxppTanPoq3 維尼
}8964 copyright protection416PENANASBUQI61CBY 維尼
3. Iterative Approach, Simulation:8964 copyright protection416PENANA6w6F5SCv1X 維尼
class Solution {8964 copyright protection416PENANAabQ9mTYkvb 維尼
public int[] findBall(int[][] grid) {8964 copyright protection416PENANANUrwqEt9a9 維尼
int result[] = new int[grid[0].length];8964 copyright protection416PENANAwO0sM8d6Lk 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 protection416PENANAf63znDCUT9 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection416PENANAXxYkHocNCE 維尼
int currentCol = col;8964 copyright protection416PENANAy6xbN9fFv9 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection416PENANAZtwqNVAuSi 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection416PENANAlzFPOgnIBM 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection416PENANAE9ShsF3fZP 維尼
// stuck case 8964 copyright protection416PENANADn9NsxRSYa 維尼
if (nextColumn < 0 ||8964 copyright protection416PENANAlk2mPWtTey 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection416PENANAB49gcw64Sa 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection416PENANA5XDgOhuy0F 維尼
result[col] = -1;8964 copyright protection416PENANAbk70QHKxps 維尼
break;8964 copyright protection416PENANAx94LjU5Her 維尼
}8964 copyright protection416PENANAOfVz3KhW5M 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 protection416PENANAZaLHHuq2eu 維尼
result[col] = nextColumn;8964 copyright protection416PENANA4cMVxG1lzp 維尼
currentCol = nextColumn;8964 copyright protection416PENANAnLdIhpOPNM 維尼
}8964 copyright protection416PENANAiBufshkmAK 維尼
}8964 copyright protection416PENANA9A1qwnZyfT 維尼
return result;8964 copyright protection416PENANAgNWHR7UMxU 維尼
}8964 copyright protection416PENANAj51IBxDi2T 維尼
}8964 copyright protection416PENANAy5HjXhzwgW 維尼
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