# Zero Matrix - Amazon Top Interview Questions

### Problem Statement :

```Given a two-dimensional matrix of integers, for each zero in the original matrix, replace all values in its row and column with zero, and return the resulting matrix.

Constraints

n * m ≤ 100,000 where n and m are the number of rows and columns in matrix

Example 1

Input

matrix = [
[5, 0, 0, 5, 8],
[9, 8, 10, 3, 9],
[0, 7, 2, 3, 1],
[8, 0, 6, 7, 2],
[4, 1, 8, 5, 10]
]

Output

[
[0, 0, 0, 0, 0],
[0, 0, 0, 3, 9],
[0, 0, 0, 0, 0],
[0, 0, 0, 0, 0],
[0, 0, 0, 5, 10]
]

Explanation

These rows contain a 0: [0, 2, 3] and the returned matrix contains 0 in those rows.

These columns contain a 0: [0, 1, 2] and the returned matrix contains 0 in those columns.```

### Solution :

```                        ```Solution in C++ :

vector<vector<int>> solve(vector<vector<int>>& matrix) {
int R = matrix.size();
int C = matrix[0].size();
if (R == 0 || C == 0) return matrix;
/// STEP 1
bool hasFirstRowZero = false;
bool hasFirstColZero = false;

// Now start from matrix(0,0)
// If first row has zero ?
for (int i = 0; i < C; i++) {
if (matrix[0][i] == 0) {
hasFirstRowZero = true;
break;
}
}

// If first column has zero ?
for (int i = 0; i < R; i++) {
if (matrix[i][0] == 0) {
hasFirstColZero = true;
break;
}
}

/// STEP 2(make use of hasFirstRowZero and hasFirstColZero)
// start from matrix(1,1) and check if matrix(i,j) is zero ?
for (int i = 1; i < R; i++) {
for (int j = 1; j < C; j++) {
if (matrix[i][j] == 0) {
matrix[i][0] = 0;  // leftmost element set 0
matrix[0][j] = 0;  // topmost element set 0
}
}
}

/// STEP 3
// start from matrix(1,1) and check topmost and leftmost element zero ?
for (int i = 1; i < R; i++) {
for (int j = 1; j < C; j++) {
if (matrix[i][0] == 0 || matrix[0][j] == 0) {
matrix[i][j] = 0;
}
}
}

/// STEP 4
// set zeroes for first row
if (hasFirstRowZero) {
for (int i = 0; i < C; i++) {
matrix[0][i] = 0;
}
}

// set zeroes for first column
if (hasFirstColZero) {
for (int i = 0; i < R; i++) {
matrix[i][0] = 0;
}
}
return matrix;
}```
```

```                        ```Solution in Java :

import java.util.*;

class Solution {
public int[][] solve(int[][] matrix) {
boolean[] rows = new boolean[matrix.length];
boolean[] cols = new boolean[matrix[0].length];

for (int i = 0; i < rows.length; i++)
for (int j = 0; j < cols.length; j++)
if (matrix[i][j] == 0) {
rows[i] = true;
cols[j] = true;
}

// Update matrix
for (int i = 0; i < rows.length; i++)
for (int j = 0; j < cols.length; j++)
if (rows[i] || cols[j])
matrix[i][j] = 0;
return matrix;
}
}```
```

```                        ```Solution in Python :

class Solution:
def solve(self, matrix):
first_row_zero = 0 in matrix[0]
first_column_zero = 0 in [matrix[i][0] for i in range(len(matrix))]
m = len(matrix)
n = len(matrix[0])
for i in range(1, m):
for j in range(1, n):
if matrix[i][j] == 0:
matrix[i][0] = 0
matrix[0][j] = 0

for i in range(1, m):
if matrix[i][0] == 0:
for j in range(1, n):
matrix[i][j] = 0

for j in range(1, n):
if matrix[0][j] == 0:
for i in range(1, m):
matrix[i][j] = 0

if first_row_zero:
matrix[0] = [0] * n

if first_column_zero:
for i in range(m):
matrix[i][0] = 0

return matrix```
```

## Left Rotation

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## Sparse Arrays

There is a collection of input strings and a collection of query strings. For each query string, determine how many times it occurs in the list of input strings. Return an array of the results. Example: strings=['ab', 'ab', 'abc'] queries=['ab', 'abc', 'bc'] There are instances of 'ab', 1 of 'abc' and 0 of 'bc'. For each query, add an element to the return array, results=[2,1,0]. Fun

## Array Manipulation

Starting with a 1-indexed array of zeros and a list of operations, for each operation add a value to each of the array element between two given indices, inclusive. Once all operations have been performed, return the maximum value in the array. Example: n=10 queries=[[1,5,3], [4,8,7], [6,9,1]] Queries are interpreted as follows: a b k 1 5 3 4 8 7 6 9 1 Add the valu

## Print the Elements of a Linked List

This is an to practice traversing a linked list. Given a pointer to the head node of a linked list, print each node's data element, one per line. If the head pointer is null (indicating the list is empty), there is nothing to print. Function Description: Complete the printLinkedList function in the editor below. printLinkedList has the following parameter(s): 1.SinglyLinkedListNode

## Insert a Node at the Tail of a Linked List

You are given the pointer to the head node of a linked list and an integer to add to the list. Create a new node with the given integer. Insert this node at the tail of the linked list and return the head node of the linked list formed after inserting this new node. The given head pointer may be null, meaning that the initial list is empty. Input Format: You have to complete the SinglyLink

## Insert a Node at the head of a Linked List

Given a pointer to the head of a linked list, insert a new node before the head. The next value in the new node should point to head and the data value should be replaced with a given value. Return a reference to the new head of the list. The head pointer given may be null meaning that the initial list is empty. Function Description: Complete the function insertNodeAtHead in the editor below