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No Plagiarism!6zQdEal7MsAq4VQlvQLuposted 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 protection378PENANAERKPM1PlXc 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 protection378PENANAvH4XJ9AluK 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 protection378PENANAIgjk6DFX7n 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 protection378PENANAdNzpMKJUPz 維尼
* [grid[0].length] = column number8964 copyright protection378PENANAbqISDYWdsZ 維尼
A: 8964 copyright protection378PENANA6wWPrB17nl 維尼
1. Depth First Search (DFS): 8964 copyright protection378PENANAlLAj4DZ83F 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 protection378PENANAdTTI53OHvD 維尼
*Using Recursive function8964 copyright protection378PENANA2YJbTXwK82 維尼
class Solution {8964 copyright protection378PENANAy0S4bijFxQ 維尼
public int[] findBall(int[][] grid) {8964 copyright protection378PENANAraxGXzobre 維尼
// create new int[], for int[grid[0].length]8964 copyright protection378PENANAZGKpIxwAjX 維尼
int result[] = new int[grid[0].length];8964 copyright protection378PENANA62M8mVq9E9 維尼
// how many ball as well as how many row8964 copyright protection378PENANA4W7vUTE801 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection378PENANA0QeYQIP0qQ 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection378PENANAG7RUXXjlzV 維尼
}8964 copyright protection378PENANAEi2WMhlx2S 維尼
return result;8964 copyright protection378PENANAhmytMdPgG9 維尼
}8964 copyright protection378PENANAwfQYVsgAep 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection378PENANAgVS2f4XWcq 維尼
// base case; ball reached the last row8964 copyright protection378PENANAukIFcf0iSk 維尼
if (row == grid.length)8964 copyright protection378PENANACEAeSJ48bW 維尼
return col;8964 copyright protection378PENANAfbdsATDMBc 維尼
int nextColumn = col + grid[row][col];8964 copyright protection378PENANA21MuRNVqPH 維尼
if (nextColumn < 0 ||8964 copyright protection378PENANAO9CHAymp6K 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection378PENANAStCnYyJLqr 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection378PENANAoY6wUZfO4b 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection378PENANAIpFn3sKHzX 維尼
return -1;8964 copyright protection378PENANAOYXWqSHFdt 維尼
}8964 copyright protection378PENANApa8mo3PPsD 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection378PENANAhHIISQg0bk 維尼
}8964 copyright protection378PENANAuMpt6E660x 維尼
}8964 copyright protection378PENANAkkCtlg5O3m 維尼
2. Dynamic Programming Approach:8964 copyright protection378PENANAQ8vphhOQEi 維尼
class Solution {8964 copyright protection378PENANAL3cNpKUabA 維尼
public int[] findBall(int[][] grid) {8964 copyright protection378PENANAq1iK2rPp8b 維尼
int result[] = new int[grid[0].length];8964 copyright protection378PENANAom6c8di3k7 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];382Please respect copyright.PENANASN0N5JssrX
8964 copyright protection378PENANAxa6ArLB3nR 維尼
382Please respect copyright.PENANA7FdnzgMTg1
8964 copyright protection378PENANA4AMCjLSKuF 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection378PENANAnkpbFB4xP1 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection378PENANAqBTQC5B7cW 維尼
if (row == grid.length) {8964 copyright protection378PENANARpDibzvszS 維尼
// for the last row 382Please respect copyright.PENANATkBvPU7uCd
8964 copyright protection378PENANAPIQK8GaaD4 維尼
memo[row][col] = col;8964 copyright protection378PENANAT17inC2aVT 維尼
continue;8964 copyright protection378PENANA8eOACcyLC6 維尼
}8964 copyright protection378PENANAXfU1LKbYuD 維尼
// for the remaining row.8964 copyright protection378PENANApi8Yk26Z3N 維尼
int nextColumn = col + grid[row][col];8964 copyright protection378PENANAOHNEvemBiH 維尼
if (nextColumn < 0 ||8964 copyright protection378PENANA9rjtFWTU3J 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection378PENANAgGJUpkR6Sn 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection378PENANAHQHcyNvDJ4 維尼
memo[row][col] = -1;8964 copyright protection378PENANAhcqSGZrrOh 維尼
else8964 copyright protection378PENANAoQ9CRVjdUm 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection378PENANAZdh5fih9c0 維尼
// reaching row 0, copy the values in all the column in the result array. 382Please respect copyright.PENANADfIGSbddab
8964 copyright protection378PENANA0jZHTzYFoz 維尼
if (row == 0) {8964 copyright protection378PENANAa552rwVSUK 維尼
result[col] = memo[row][col];8964 copyright protection378PENANAXZgrNMzzYg 維尼
}8964 copyright protection378PENANAsqnimwppTk 維尼
}8964 copyright protection378PENANAZquOMX8CpG 維尼
}8964 copyright protection378PENANAngc2AmpHWs 維尼
return result;8964 copyright protection378PENANAogH7NLgUw3 維尼
}8964 copyright protection378PENANACf7B6eDZXr 維尼
}8964 copyright protection378PENANABOBwjDvo4f 維尼
3. Iterative Approach, Simulation:8964 copyright protection378PENANA7cOLNpzCGU 維尼
class Solution {8964 copyright protection378PENANAiKMxRD9uus 維尼
public int[] findBall(int[][] grid) {8964 copyright protection378PENANA9XXLpwCRgQ 維尼
int result[] = new int[grid[0].length];8964 copyright protection378PENANAyQ5N6FEvF4 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 protection378PENANAcsajHRTKft 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection378PENANA0bnChc789l 維尼
int currentCol = col;8964 copyright protection378PENANAoJoeiwrark 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection378PENANAotxbAU0pL8 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection378PENANAyjPWhp9Pd8 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection378PENANAvXIWZhD3h8 維尼
// stuck case 8964 copyright protection378PENANA5XqJkXypST 維尼
if (nextColumn < 0 ||8964 copyright protection378PENANATqTUBcuGCy 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection378PENANAz3S7KiFkn5 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection378PENANACntEre3xY3 維尼
result[col] = -1;8964 copyright protection378PENANAL2IRqnm2dT 維尼
break;8964 copyright protection378PENANAwIOhwrdUiZ 維尼
}8964 copyright protection378PENANAsVeNqIzfOi 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 protection378PENANAxKBHJNVLkN 維尼
result[col] = nextColumn;8964 copyright protection378PENANAwO6e80aCZO 維尼
currentCol = nextColumn;8964 copyright protection378PENANAk7tz2wzymX 維尼
}8964 copyright protection378PENANApdZLPTPne0 維尼
}8964 copyright protection378PENANAu1OQN7Z6vu 維尼
return result;8964 copyright protection378PENANAr9yBgHM0Jq 維尼
}8964 copyright protection378PENANA5Fci0lBHgn 維尼
}8964 copyright protection378PENANAkgIcQLItTE 維尼
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