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No Plagiarism!qu1lg11Cs1lu2gqsXZ40posted 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 protection233PENANAehTrLK3Ot2 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 protection233PENANAM8THwbCvfG 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 protection233PENANA9VaYss9wVi 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 protection233PENANAaYam47i1NF 維尼
* [grid[0].length] = column number8964 copyright protection233PENANAR8f3SeuxWR 維尼
A: 8964 copyright protection233PENANAcSEjnB3bBl 維尼
1. Depth First Search (DFS): 8964 copyright protection233PENANANKXzrcbXIC 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 protection233PENANAIFb20Nslzj 維尼
*Using Recursive function8964 copyright protection233PENANA7obqpCYvos 維尼
class Solution {8964 copyright protection233PENANAkRUIAw8mt1 維尼
public int[] findBall(int[][] grid) {8964 copyright protection233PENANAV8rijdHaqw 維尼
// create new int[], for int[grid[0].length]8964 copyright protection233PENANAR13Xmw54iH 維尼
int result[] = new int[grid[0].length];8964 copyright protection233PENANAmmRA45f6js 維尼
// how many ball as well as how many row8964 copyright protection233PENANAYmzsGBHRfV 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection233PENANAfw795EEdWf 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection233PENANASRhv1jWDLh 維尼
}8964 copyright protection233PENANASbjdw37htQ 維尼
return result;8964 copyright protection233PENANAtIiDl5lqjQ 維尼
}8964 copyright protection233PENANAg2oocE67RU 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection233PENANADTTHrdZeZ8 維尼
// base case; ball reached the last row8964 copyright protection233PENANAMQjOKbRwzh 維尼
if (row == grid.length)8964 copyright protection233PENANArPq0fYBSXV 維尼
return col;8964 copyright protection233PENANAzIiAhYJcJA 維尼
int nextColumn = col + grid[row][col];8964 copyright protection233PENANAxlwrZdGtoE 維尼
if (nextColumn < 0 ||8964 copyright protection233PENANAvZRSSlJZuD 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection233PENANA14L76Y5dAw 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection233PENANAkp1mWQNf4G 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection233PENANAkX1QnK3zdd 維尼
return -1;8964 copyright protection233PENANAOut83jlNvz 維尼
}8964 copyright protection233PENANAsyIPoTb2aO 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection233PENANAocx9qNs5Vf 維尼
}8964 copyright protection233PENANAuNkdDXm6cr 維尼
}8964 copyright protection233PENANALou3Mc9WbV 維尼
2. Dynamic Programming Approach:8964 copyright protection233PENANAWD7pGED8hm 維尼
class Solution {8964 copyright protection233PENANAZQ8x3aHTDS 維尼
public int[] findBall(int[][] grid) {8964 copyright protection233PENANA8TFUzaveJT 維尼
int result[] = new int[grid[0].length];8964 copyright protection233PENANA2jZoDa6coZ 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];237Please respect copyright.PENANA5puPXTquUe
8964 copyright protection233PENANAxjndGJTyYu 維尼
237Please respect copyright.PENANArpAVneOU1N
8964 copyright protection233PENANA9klWj5QmeG 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection233PENANAgdkrhevzhg 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection233PENANASdiVSimwd8 維尼
if (row == grid.length) {8964 copyright protection233PENANAmCYST1o1sK 維尼
// for the last row 237Please respect copyright.PENANAaDwxgepJuh
8964 copyright protection233PENANAtRGJl9vJFJ 維尼
memo[row][col] = col;8964 copyright protection233PENANAFgRqLoxZpC 維尼
continue;8964 copyright protection233PENANAjLawYyWQuP 維尼
}8964 copyright protection233PENANAWR8SELR03l 維尼
// for the remaining row.8964 copyright protection233PENANAbpY4uKmEuL 維尼
int nextColumn = col + grid[row][col];8964 copyright protection233PENANAfCCilRpmxg 維尼
if (nextColumn < 0 ||8964 copyright protection233PENANAQq1xBlIcFD 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection233PENANASNZ6buSgm7 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection233PENANA6s2YPFaFMM 維尼
memo[row][col] = -1;8964 copyright protection233PENANAQnVjKhlMai 維尼
else8964 copyright protection233PENANAXcKaHpUoQN 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection233PENANAzG3TRgGno5 維尼
// reaching row 0, copy the values in all the column in the result array. 237Please respect copyright.PENANARO7AKdOe5l
8964 copyright protection233PENANAc7pw3PXqeC 維尼
if (row == 0) {8964 copyright protection233PENANASTlCc65f83 維尼
result[col] = memo[row][col];8964 copyright protection233PENANA6v0svl4I8M 維尼
}8964 copyright protection233PENANAjuXthewCM3 維尼
}8964 copyright protection233PENANA0QsrI1KrNE 維尼
}8964 copyright protection233PENANAmW7QJ6iqyC 維尼
return result;8964 copyright protection233PENANAeqRQGlvflx 維尼
}8964 copyright protection233PENANA6T2D92lQJq 維尼
}8964 copyright protection233PENANAtre3TVJCfI 維尼
3. Iterative Approach, Simulation:8964 copyright protection233PENANAhbXPBMKYNh 維尼
class Solution {8964 copyright protection233PENANAVnSd63rIAj 維尼
public int[] findBall(int[][] grid) {8964 copyright protection233PENANAzfekfLtfiw 維尼
int result[] = new int[grid[0].length];8964 copyright protection233PENANA3syQJE5yuL 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 protection233PENANAwpFXCl8k4B 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection233PENANANokhpTu6iS 維尼
int currentCol = col;8964 copyright protection233PENANAliGqnPjuuG 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection233PENANA8drOjB3Hea 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection233PENANArGdkFPMTX7 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection233PENANArmjw7lUw36 維尼
// stuck case 8964 copyright protection233PENANAKmrbrG3Ja1 維尼
if (nextColumn < 0 ||8964 copyright protection233PENANAGWIxucpNQF 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection233PENANAPDLW3pmCpL 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection233PENANALTiw52WGGR 維尼
result[col] = -1;8964 copyright protection233PENANAezt5tpaNJx 維尼
break;8964 copyright protection233PENANASEesddAEUj 維尼
}8964 copyright protection233PENANAtGolSUMBoJ 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 protection233PENANAbsZuAWTTfv 維尼
result[col] = nextColumn;8964 copyright protection233PENANAxtSCepxNBE 維尼
currentCol = nextColumn;8964 copyright protection233PENANASS59kEnC7I 維尼
}8964 copyright protection233PENANAXiLVyZBzgy 維尼
}8964 copyright protection233PENANAztz4J9vSNT 維尼
return result;8964 copyright protection233PENANAbaUCGwvCmJ 維尼
}8964 copyright protection233PENANAimVis02xsl 維尼
}8964 copyright protection233PENANAiliwsX2Zvw 維尼
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