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No Plagiarism!7tCuyoqNL7CGuFXr5ldNposted 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 protection428PENANApn8k1z4PjF 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 protection428PENANACvep7qBaB7 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 protection428PENANArTy0pqRwp1 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 protection428PENANAq9LP008Dwx 維尼
* [grid[0].length] = column number8964 copyright protection428PENANA6QPJpuBEiV 維尼
A: 8964 copyright protection428PENANAox3exN2nsL 維尼
1. Depth First Search (DFS): 8964 copyright protection428PENANAKBnxJoCgkp 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 protection428PENANAVLXSGhKtLi 維尼
*Using Recursive function8964 copyright protection428PENANAIihqaSr4mD 維尼
class Solution {8964 copyright protection428PENANAl7ym8h5jV9 維尼
public int[] findBall(int[][] grid) {8964 copyright protection428PENANAa9xNsey1Ki 維尼
// create new int[], for int[grid[0].length]8964 copyright protection428PENANAsrKIKWaeaw 維尼
int result[] = new int[grid[0].length];8964 copyright protection428PENANAo6FAhTXAWA 維尼
// how many ball as well as how many row8964 copyright protection428PENANAanKof8hKqE 維尼
for (int i = 0; i < grid[0].length; i++) {8964 copyright protection428PENANAojwL1mxnZp 維尼
result[i] = findBallDropColumn(0, i, grid);8964 copyright protection428PENANA5kuqWEIjYM 維尼
}8964 copyright protection428PENANAEwuJMbMEgQ 維尼
return result;8964 copyright protection428PENANAcsWphrMhb2 維尼
}8964 copyright protection428PENANAh6y5YOS8Ji 維尼
public int findBallDropColumn(int row, int col, int[][] grid) {8964 copyright protection428PENANAdoYVvHJTrh 維尼
// base case; ball reached the last row8964 copyright protection428PENANAvF9nuuc2P7 維尼
if (row == grid.length)8964 copyright protection428PENANAQPK0oDfxoN 維尼
return col;8964 copyright protection428PENANApelJgrulwD 維尼
int nextColumn = col + grid[row][col];8964 copyright protection428PENANAsWD82jHObI 維尼
if (nextColumn < 0 ||8964 copyright protection428PENANAdqChIpXD7a 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection428PENANALzvTmTQklH 維尼
// [1,1] & [-1,-1]drop, [1,-1] & [-1,1] stuck8964 copyright protection428PENANAqXKGvuCkQQ 維尼
grid[row][col] != grid[row][nextColumn]) {8964 copyright protection428PENANAqHjtpLADTs 維尼
return -1;8964 copyright protection428PENANAI8aSnqJ3SV 維尼
}8964 copyright protection428PENANAjlvvCz4yrn 維尼
return findBallDropColumn(row + 1, nextColumn, grid);8964 copyright protection428PENANA3fInjpXVys 維尼
}8964 copyright protection428PENANAxwwyahMvWv 維尼
}8964 copyright protection428PENANA1vGCeuHciy 維尼
2. Dynamic Programming Approach:8964 copyright protection428PENANAPm7paZ9ifu 維尼
class Solution {8964 copyright protection428PENANAlnCriAPbQ0 維尼
public int[] findBall(int[][] grid) {8964 copyright protection428PENANAgfCfwAnAtG 維尼
int result[] = new int[grid[0].length];8964 copyright protection428PENANAjNgz5cML50 維尼
Integer memo[][] = new Integer[grid.length + 1][grid[0].length];432Please respect copyright.PENANA0z2P4BsdZK
8964 copyright protection428PENANA7y1HVEM5JD 維尼
432Please respect copyright.PENANAmVb1iQIYrd
8964 copyright protection428PENANANdIiWcyOcu 維尼
for (int row = grid.length; row >= 0; row--) {8964 copyright protection428PENANAwShyPtSCgP 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection428PENANAHnxqGLPgF4 維尼
if (row == grid.length) {8964 copyright protection428PENANAjKkx3mPBp8 維尼
// for the last row 432Please respect copyright.PENANAv6tV7xIDUx
8964 copyright protection428PENANA6MjTurCf40 維尼
memo[row][col] = col;8964 copyright protection428PENANA1nD4MbYdFQ 維尼
continue;8964 copyright protection428PENANAWs1TZNvXWt 維尼
}8964 copyright protection428PENANAidGZiyjire 維尼
// for the remaining row.8964 copyright protection428PENANAAFaHYpgA3M 維尼
int nextColumn = col + grid[row][col];8964 copyright protection428PENANAsayEugESZy 維尼
if (nextColumn < 0 ||8964 copyright protection428PENANAOoEz00IMLb 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection428PENANAsbqTyUIEYQ 維尼
grid[row][col] != grid[row][nextColumn])8964 copyright protection428PENANAcKAYGWqNmS 維尼
memo[row][col] = -1;8964 copyright protection428PENANAjveht36Zo0 維尼
else8964 copyright protection428PENANAlY7LEC4Nae 維尼
memo[row][col] = memo[row + 1][nextColumn];8964 copyright protection428PENANAimyce4wsTZ 維尼
// reaching row 0, copy the values in all the column in the result array. 432Please respect copyright.PENANAD3r2u0q9fQ
8964 copyright protection428PENANAKfMBZoOUbL 維尼
if (row == 0) {8964 copyright protection428PENANAP5Bce2SA6p 維尼
result[col] = memo[row][col];8964 copyright protection428PENANA31ZSMXvnN3 維尼
}8964 copyright protection428PENANAoGLHIOeWHM 維尼
}8964 copyright protection428PENANAxOzV7fFANf 維尼
}8964 copyright protection428PENANAWh5hMNbIXu 維尼
return result;8964 copyright protection428PENANArSM0qg0KX6 維尼
}8964 copyright protection428PENANA7Zre0WLICR 維尼
}8964 copyright protection428PENANAFZFiYAUgiM 維尼
3. Iterative Approach, Simulation:8964 copyright protection428PENANAhttj1s9Tpq 維尼
class Solution {8964 copyright protection428PENANASSFnxyko4d 維尼
public int[] findBall(int[][] grid) {8964 copyright protection428PENANAPPKDb8aaKA 維尼
int result[] = new int[grid[0].length];8964 copyright protection428PENANAixE4twko2B 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 protection428PENANAq6SrAWbbHh 維尼
for (int col = 0; col < grid[0].length; col++) {8964 copyright protection428PENANABZwoFoMWc5 維尼
int currentCol = col;8964 copyright protection428PENANApkEgifGqSJ 維尼
// 2. For every such ball, simulate its movement in every row ranging from the 0th to the nth row.8964 copyright protection428PENANAA15cKWQxDK 維尼
for (int row = 0; row < grid.length; row++) {8964 copyright protection428PENANAqB7SGloGcj 維尼
int nextColumn = currentCol + grid[row][currentCol];8964 copyright protection428PENANAlVHEH2wGSZ 維尼
// stuck case 8964 copyright protection428PENANASFBOs58Jyz 維尼
if (nextColumn < 0 ||8964 copyright protection428PENANAydtYoGZOJB 維尼
nextColumn > grid[0].length - 1 ||8964 copyright protection428PENANA68Qjm6RtKS 維尼
grid[row][currentCol] != grid[row][nextColumn]) {8964 copyright protection428PENANAon3ShVvzKu 維尼
result[col] = -1;8964 copyright protection428PENANAPfDJFjvBSQ 維尼
break;8964 copyright protection428PENANAU5BWh00yCJ 維尼
}8964 copyright protection428PENANAWa4TcqiQIQ 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 protection428PENANAgtdxGuYzuM 維尼
result[col] = nextColumn;8964 copyright protection428PENANAHdo7ckYbMl 維尼
currentCol = nextColumn;8964 copyright protection428PENANAb6XpUS4CCB 維尼
}8964 copyright protection428PENANAXT6plmu0y3 維尼
}8964 copyright protection428PENANAS67YvAvEQA 維尼
return result;8964 copyright protection428PENANA43RQNhP9TW 維尼
}8964 copyright protection428PENANAEjWPtCXaYI 維尼
}8964 copyright protection428PENANAMBTOGu0XBY 維尼
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