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No Plagiarism!misQ08lwVxgg4l4VtAgvposted 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 protection232PENANAEwEmHtjTzK 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 protection232PENANAQEp8B2M3XO 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 protection232PENANA15teBgnGT8 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 protection232PENANAfkPJ32sDBN 維尼
* [grid[0].length] = column number8964 copyright protection232PENANAIwFK7xRzqE 維尼
A: 8964 copyright protection232PENANA2KdOSqnflQ 維尼
1. Depth First Search (DFS): 8964 copyright protection232PENANANrvp9dC2Cd 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 protection232PENANAHhJsbRZoxG 維尼
*Using Recursive function8964 copyright protection232PENANADuZnJqGmzq 維尼
class Solution {8964 copyright protection232PENANAp0C1PqrdaC 維尼
public int[] findBall(int[][] grid) {8964 copyright protection232PENANAarg87CDvsE 維尼
// create new int[], for int[grid[0].length]8964 copyright protection232PENANAd2au4SKSnF 維尼
int result[] = new int[grid[0].length];8964 copyright protection232PENANA9nep20ICs7 維尼
// how many ball as well as how many row8964 copyright protection232PENANA4ZWYWpOD3e 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection232PENANAsHRfYtGgN3 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection232PENANAIHNdju0kqC 維尼
}8964 copyright protection232PENANApXl0G8iXWc 維尼
return result;8964 copyright protection232PENANARO0IoLZtru 維尼
}8964 copyright protection232PENANA6HyBRHLsMT 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection232PENANA2feeZUnDuJ 維尼
// base case; ball reached the last row8964 copyright protection232PENANAKM2bFj2VQv 維尼
if (row == grid.length)8964 copyright protection232PENANAsrVVWZKhl6 維尼
return col;8964 copyright protection232PENANAsDTW9oBzNr 維尼
int nextColumn = col + grid[row][col];8964 copyright protection232PENANARsDhR25ukm 維尼
if (nextColumn < 0 ||8964 copyright protection232PENANALRxrSeUB87 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection232PENANAtX90zhDV0v 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection232PENANAcH1V2EmMnI 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection232PENANAhEuQxGk6xS 維尼
return -1;8964 copyright protection232PENANAFJPV4G2znH 維尼
}8964 copyright protection232PENANAhTjroUJh9S 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection232PENANAsT2fJvqrW5 維尼
}8964 copyright protection232PENANAdy5bb9qZai 維尼
}8964 copyright protection232PENANA3r72VMmHyE 維尼
2. Dynamic Programming Approach:8964 copyright protection232PENANA9m87xF4DPq 維尼
class Solution {8964 copyright protection232PENANAv7pJepGJMO 維尼
public int[] findBall(int[][] grid) {8964 copyright protection232PENANAmXT3l9XF7X 維尼
int result[] = new int[grid[0].length];8964 copyright protection232PENANA1dV6EuFiI0 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];236Please respect copyright.PENANApxniojNRyv
8964 copyright protection232PENANA2tpxdpnDst 維尼
236Please respect copyright.PENANAiKgWBAg157
8964 copyright protection232PENANAiidO1VjVMq 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection232PENANAh8QJW6BRty 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection232PENANAbExISYcfGP 維尼
if (row == grid.length) {8964 copyright protection232PENANA7orf1pFKfZ 維尼
// for the last row 236Please respect copyright.PENANAVmR1gw4HyS
8964 copyright protection232PENANAN7fabMTG43 維尼
memo[row][col] = col;8964 copyright protection232PENANAgSqjnpQktB 維尼
continue;8964 copyright protection232PENANAF7v9IP5yTh 維尼
}8964 copyright protection232PENANAdfVpLJjqGq 維尼
// for the remaining row.8964 copyright protection232PENANA74J5OSHgQf 維尼
int nextColumn = col + grid[row][col];8964 copyright protection232PENANARaIdq0YQkw 維尼
if (nextColumn < 0 ||8964 copyright protection232PENANAxruxjNLBGM 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection232PENANAzHurUYP5Pu 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection232PENANALXqU7XWbGD 維尼
memo[row][col] = -1;8964 copyright protection232PENANA7LdcPdccLd 維尼
else8964 copyright protection232PENANALwp7cpHhmE 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection232PENANAMO22x8BLkC 維尼
// reaching row 0, copy the values in all the column in the result array. 236Please respect copyright.PENANAwGYQAgs9iw
8964 copyright protection232PENANASOl58SLkYm 維尼
if (row == 0) {8964 copyright protection232PENANAAAEIDqpxT4 維尼
result[col] = memo[row][col];8964 copyright protection232PENANAjp3pz9AhXB 維尼
}8964 copyright protection232PENANAUcbNSxCamI 維尼
}8964 copyright protection232PENANAMca4xCHWzs 維尼
}8964 copyright protection232PENANAigNoAaQhJY 維尼
return result;8964 copyright protection232PENANArB7W8b6lTj 維尼
}8964 copyright protection232PENANA7FybFyxIV4 維尼
}8964 copyright protection232PENANAZNiq75DBY0 維尼
3. Iterative Approach, Simulation:8964 copyright protection232PENANAKG25YBvFDv 維尼
class Solution {8964 copyright protection232PENANAd1l9wiPygB 維尼
public int[] findBall(int[][] grid) {8964 copyright protection232PENANAIOZHySwvYx 維尼
int result[] = new int[grid[0].length];8964 copyright protection232PENANAZstkpAoKqE 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 protection232PENANAy2zBEfo13d 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection232PENANAzWDPWvze3o 維尼
int currentCol = col;8964 copyright protection232PENANAbyw1amrjud 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection232PENANATwHTQBIssL 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection232PENANATzTrgLGcT7 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection232PENANAY1Wc7ZGuZX 維尼
// stuck case 8964 copyright protection232PENANALabYFYywGs 維尼
if (nextColumn < 0 ||8964 copyright protection232PENANA6rvCKFoHQc 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection232PENANAKcdYfKLyCo 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection232PENANAemEP25725F 維尼
result[col] = -1;8964 copyright protection232PENANAE1vkBYPgck 維尼
break;8964 copyright protection232PENANAx99MThPwF6 維尼
}8964 copyright protection232PENANAfXcCIw5rgE 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 protection232PENANAxAaQDfsA3Y 維尼
result[col] = nextColumn;8964 copyright protection232PENANA7Lx7fsFhZA 維尼
currentCol = nextColumn;8964 copyright protection232PENANAAwMbDlag5L 維尼
}8964 copyright protection232PENANAVbsMi6lYVA 維尼
}8964 copyright protection232PENANAt2z7MwDTEs 維尼
return result;8964 copyright protection232PENANAL2kLpNigFQ 維尼
}8964 copyright protection232PENANAlesc53y17J 維尼
}8964 copyright protection232PENANAFBOAZiYoDc 維尼
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