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Leetcode with dani
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🏆 LeetCode 490. The Maze (Premium) 🏆

There's a ball in a maze with:
- Empty spaces (0) and walls (1).

The ball can roll in any direction:
- Up, down, left, or right 🌐

But here's the catch:
- It won't stop until it hits a wall! 🚧
- Once it stops, it can choose another direction to roll.

### Task 🎯
Given:
- An m x n maze
- The ball's starting position and a destination

Determine:
- Can the ball stop at the destination?
- If yes, return true. Otherwise, return false.

📝 Assumption: All borders of the maze are walls.

---

### Examples 🔍

Example 1:

Input: 
maze = [
[0,0,1,0,0],
[0,0,0,0,0],
[0,0,0,1,0],
[1,1,0,1,1],
[0,0,0,0,0]
],
start = [0,4],
destination = [4,4]

Output: true

Explanation: One possible path: left ➡️ down ➡️ left ➡️ down ➡️ right ➡️ down ➡️ right 🎯

---

Example 2:

Input:
maze = [
[0,0,1,0,0],
[0,0,0,0,0],
[0,0,0,1,0],
[1,1,0,1,1],
[0,0,0,0,0]
],
start = [0,4],
destination = [3,2]

Output: false

Explanation: The ball can pass through the destination, but it cannot stop there.

---

Example 3:

Input:
maze = [
[0,0,0,0,0],
[1,1,0,0,1],
[0,0,0,0,0],
[0,1,0,0,1],
[0,1,0,0,0]
],
start = [4,3],
destination = [0,1]

Output: false


---

### Constraints 📏
- Maze Dimensions: 1 ≤ m, n ≤ 100
- Cells contain only 0 (empty) or 1 (wall).
- Start and destination are in empty spaces and won’t initially overlap.

Can you solve it? 🤔
👍321🤯1
Forwarded from LeetCode VIP
Forwarded from LeetCode VIP
🔥4👍1
Leetcode with dani
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share ur answer in the comment section , i will check it
Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number.

Example:

Input : n =10
Output : 2 3 5 7


Input : n = 20
Output: 2 3 5 7 11 13 17 19
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Sieve of Eratosthenes

Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number.

Example:

Input : n =10
Output : 2 3 5 7


Input : n = 20
Output: 2 3 5 7 11 13 17 19

The sieve of Eratosthenes is one of the most efficient ways to find all primes smaller than n when n is smaller than 10 million or so.

Following is the algorithm to find all the prime numbers less than or equal to a given integer n by the Eratosthene’s method:
When the algorithm terminates, all the numbers in the list that are not marked are prime.

Explanation with Example:
Let us take an example when n = 100. So, we need to print all prime numbers smaller than or equal to 100.


We create a list of all numbers from 2 to 100.
According to the algorithm we will mark all the numbers which are divisible by 2 and are greater than or equal to the square of it.
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Now we move to our next unmarked number 3 and mark all the numbers which are multiples of 3 and are greater than or equal to the square of it.
We move to our next unmarked number 5 and mark all multiples of 5 and are greater than or equal to the square of it.
We continue this process, and our final table will look like below:
So, the prime numbers are the unmarked ones: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.
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🎯 Problem of the Day: Sort Colors

Problem Denoscription
You are given an array nums with \( n \) objects colored red, white, or blue. Sort the array in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.
- Represent the colors using integers:
- 0 → Red
- 1 → White
- 2 → Blue

⚠️ Note: You must not use the library's sort function.

---

Example 1
Input:
nums = [2,0,2,1,1,0]

Output:
[0,0,1,1,2,2]


Example 2
Input:
nums = [2,0,1]

Output:
[0,1,2]


---

📝 Practice Questions for A2SV Preparation
1. Core Problem:
- Solve LeetCode 75: Sort Colors () using Dutch National Flag Algorithm for \( O(n) \) time complexity.

2. Related Problems:
- LeetCode 215 : Kth Largest Element in an Array
- LeetCode 347 : Top K Frequent Elements
- LeetCode 56 : Merge Intervals

3. Challenge Problem:
- LeetCode 88: Merge Sorted Array

---

💡 Tip: Use a two-pointer or three-pointer approach to keep track of boundaries for the different colors! Try to optimize your solution to \( O(n) \) in both time and space.

🧠 Share your solution and discuss your approach with the community! 🌟
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238. Product of Array Except Self
Difficulty: Medium

Problem:
Given an integer array nums, return an array answer such that answer[i] is the product of all elements of nums except nums[i].

Conditions:
- The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
- Your algorithm must run in O(n) time and must not use the division operation.

Examples:
Input: nums = [1,2,3,4]
Output: [24,12,8,6]

Input: nums = [-1,1,0,-3,3]
Output: [0,0,9,0,0]

Constraints:
2 <= nums.length <= 10^5
-30 <= nums[i] <= 30

Can you solve it?
👍3
Question: Can You Make This String a Palindrome?

A palindrome is a string that reads the same forwards and backwards. Given a string, determine if it's possible to rearrange the characters to form a palindrome.

Examples:

1. Input: "civic"

Output: True

Explanation: The string is already a palindrome.

2. Input: "ivicc"

Output: True

Explanation: Rearranging the characters can form the palindrome "civic".

3. Input: "hello"

Output: False

Explanation: No rearrangement can form a palindrome.

4. Input: "aabbcc"

Output: True

Explanation: Rearranging the characters can form the palindrome "abcba".

5. Input: "racecar"

Output: True

Explanation: The string is already a palindrome.

Challenge:
Write a function that takes a string as input and returns True if the string can be rearranged to form a palindrome, and False otherwise.
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