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No Plagiarism!FnDjWwkCOLuMHu0qWHjwposted 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 protection237PENANAh3IEj14Ndb 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 protection237PENANAPxqp3Bct9d 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 protection237PENANAhCcv1eKNZe 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 protection237PENANAzjSxpT50fI 維尼
* [grid[0].length] = column number8964 copyright protection237PENANAibbUkX3kvt 維尼
A: 8964 copyright protection237PENANARRrEfSkwh3 維尼
1. Depth First Search (DFS): 8964 copyright protection237PENANAYJKz7KpQBe 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 protection237PENANA3bJWXiBH60 維尼
*Using Recursive function8964 copyright protection237PENANAnrI0rr6meZ 維尼
class Solution {8964 copyright protection237PENANAgMajqfkUkO 維尼
public int[] findBall(int[][] grid) {8964 copyright protection237PENANAaMdY4bFjgG 維尼
// create new int[], for int[grid[0].length]8964 copyright protection237PENANAhM6FrqXX96 維尼
int result[] = new int[grid[0].length];8964 copyright protection237PENANAy62sNiV5U8 維尼
// how many ball as well as how many row8964 copyright protection237PENANALn6PlnhxR6 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection237PENANAcd1MUDkeuL 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection237PENANAlVJyrRtRhy 維尼
}8964 copyright protection237PENANAZ3sfZ1KkG7 維尼
return result;8964 copyright protection237PENANAwnXCzcECOR 維尼
}8964 copyright protection237PENANAK65FwlaY3T 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection237PENANA4f72h5OexB 維尼
// base case; ball reached the last row8964 copyright protection237PENANAOQVxDWyGRh 維尼
if (row == grid.length)8964 copyright protection237PENANAKNZrXAhaVg 維尼
return col;8964 copyright protection237PENANA711e6a8cMP 維尼
int nextColumn = col + grid[row][col];8964 copyright protection237PENANAMosfj15Wq9 維尼
if (nextColumn < 0 ||8964 copyright protection237PENANAEkoHiA9d7n 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection237PENANAP6eVVeguBQ 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection237PENANAw3rcBMOtg2 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection237PENANA0mWxjHpZqU 維尼
return -1;8964 copyright protection237PENANAJjdxfINpRW 維尼
}8964 copyright protection237PENANAHA6q1bhlwJ 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection237PENANA4tKzF6PvOb 維尼
}8964 copyright protection237PENANA8GLiooOQJ8 維尼
}8964 copyright protection237PENANAWQnBYyl2M0 維尼
2. Dynamic Programming Approach:8964 copyright protection237PENANASQRk6mcxKu 維尼
class Solution {8964 copyright protection237PENANAGaV81xfSA8 維尼
public int[] findBall(int[][] grid) {8964 copyright protection237PENANANTQFgRwrXp 維尼
int result[] = new int[grid[0].length];8964 copyright protection237PENANA6ilWxBTVCF 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];241Please respect copyright.PENANAJQ6ItGkbb4
8964 copyright protection237PENANADsP0x09tRx 維尼
241Please respect copyright.PENANAQ5NmjFcmfc
8964 copyright protection237PENANAcpuRistcOI 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection237PENANAHMajUBYXny 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection237PENANAVJEoEdMi1y 維尼
if (row == grid.length) {8964 copyright protection237PENANAETrfyETzT5 維尼
// for the last row 241Please respect copyright.PENANAhscDjrN3Y4
8964 copyright protection237PENANA1DeotUUZhc 維尼
memo[row][col] = col;8964 copyright protection237PENANAHLmsxwc4BM 維尼
continue;8964 copyright protection237PENANA5qlucnMyrH 維尼
}8964 copyright protection237PENANARqUoSbuCoB 維尼
// for the remaining row.8964 copyright protection237PENANAEEr0sGarO1 維尼
int nextColumn = col + grid[row][col];8964 copyright protection237PENANAOyfKSBk1dy 維尼
if (nextColumn < 0 ||8964 copyright protection237PENANAo8c4IlHEqF 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection237PENANAyQPrxIKsmB 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection237PENANApGhwC5iCEN 維尼
memo[row][col] = -1;8964 copyright protection237PENANAdTPJR09JUy 維尼
else8964 copyright protection237PENANAekeCvjHI4y 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection237PENANAiJH9dZZLkr 維尼
// reaching row 0, copy the values in all the column in the result array. 241Please respect copyright.PENANACexuUZptJH
8964 copyright protection237PENANAYtRJ2h7oGW 維尼
if (row == 0) {8964 copyright protection237PENANASLcIRwpYmv 維尼
result[col] = memo[row][col];8964 copyright protection237PENANAGEiouo0PKM 維尼
}8964 copyright protection237PENANAiBZh1ni07D 維尼
}8964 copyright protection237PENANADubLqChYzW 維尼
}8964 copyright protection237PENANAXsZip5YcLO 維尼
return result;8964 copyright protection237PENANAQyNBXynSF6 維尼
}8964 copyright protection237PENANAf1Jo68xf8E 維尼
}8964 copyright protection237PENANAqN5ePzKaM4 維尼
3. Iterative Approach, Simulation:8964 copyright protection237PENANAhxxgzxPEZK 維尼
class Solution {8964 copyright protection237PENANAckI4gLRJiw 維尼
public int[] findBall(int[][] grid) {8964 copyright protection237PENANAU4IiL3y3IR 維尼
int result[] = new int[grid[0].length];8964 copyright protection237PENANAWuJ7wDJP3B 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 protection237PENANAj8lCjIKzgc 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection237PENANATwctNMmZ91 維尼
int currentCol = col;8964 copyright protection237PENANACOlRCXiBFZ 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection237PENANAKzrFxz0a1M 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection237PENANA9iJszsQbto 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection237PENANAd4cGgnnxgu 維尼
// stuck case 8964 copyright protection237PENANAalRCu9d6Rz 維尼
if (nextColumn < 0 ||8964 copyright protection237PENANAhf4X0TkY72 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection237PENANAR0guf7MHtT 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection237PENANA4huXQKkU5L 維尼
result[col] = -1;8964 copyright protection237PENANArKgZ4jV47o 維尼
break;8964 copyright protection237PENANAFklzVK40I9 維尼
}8964 copyright protection237PENANAKRhBrOxZLG 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 protection237PENANAQ04ouq5dVU 維尼
result[col] = nextColumn;8964 copyright protection237PENANAdmpXcJLuqf 維尼
currentCol = nextColumn;8964 copyright protection237PENANAO87CYccQy9 維尼
}8964 copyright protection237PENANA8oZiWzP28z 維尼
}8964 copyright protection237PENANAtjK5FI1gZy 維尼
return result;8964 copyright protection237PENANAK7sNDYUXul 維尼
}8964 copyright protection237PENANA0n2AYZFFYN 維尼
}8964 copyright protection237PENANADR1PH6N2GE 維尼
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