[Geeks for Geeks Solution]: Fascinating Number

dsa-solutions/gfg-solutions/0001-value-equal-to-index-value.md

@@ -47,8 +47,8 @@ You don't need to read input or print anything. Your task is to complete the fun
 
 ## Constraints
 
-* 1 ≤ N ≤ 105
-* 1 ≤ `Arr[i]` ≤ 106
+* `1 ≤ N ≤ 105`
+* `1 ≤ Arr[i] ≤ 106`
 
 ## Problem Explanation
 

dsa-solutions/gfg-solutions/0002-fascinating-number.md

@@ -0,0 +1,144 @@
+---
+id: fascinating-number
+title: Fascinating Number Problem (Geeks for Geeks)
+sidebar_label: 0002 - Fascinating Number 
+tags:
+  - Beginner
+  - String
+  - Find
+  - Multiplication
+  - Geeks for Geeks
+  - CPP
+  - Python
+  - DSA
+description: "This is a solution to the Fascinating Number problem on Geeks for Geeks."
+---
+
+This tutorial contains a complete walk-through of the Fascinating Number problem from the Geeks for Geeks website. It features the implementation of the solution code in two programming languages: Python and C++.
+
+## Problem Description
+
+Given a number N. Your task is to check whether it is fascinating or not.
+
+Fascinating Number: When a number(should contain 3 digits or more) is multiplied by 2 and 3, and when both these products are concatenated with the original number, then it results in all digits from 1 to 9 present exactly once.
+
+## Examples
+
+**Example 1:**
+
+```
+Input: N = 192
+Output: Fascinating
+Explanation: After multiplication with 2 and 3, and concatenating with original number, number will become 192384576 which contains all digits from 1 to 9.
+```
+
+**Example 2:**
+
+```
+Input: N = 853
+Output: Not Fascinating
+Explanation: It's not a fascinating number.
+```
+
+## Your Task
+
+You don't need to read input or print anything. Your task is to complete the function `fascinating()` which takes the integer n parameters and returns boolean (True or False) denoting the answer.
+
+Expected Time Complexity: $O(1)$
+Expected Auxiliary Space: $O(1)$
+
+## Constraints
+
+`100 <= N <= 2*10^9`
+
+## Problem Explanation
+
+The problem is to determine if a given number N is a fascinating number. A fascinating number is defined as follows:
+
+1. The number must have at least three digits.
+2. Multiply the number by 2 and 3 to get two products.
+3. Concatenate the original number, the product of the number and 2, and the product of the number and 3 into a single string.
+4. The concatenated string should contain all digits from 1 to 9 exactly once, with no other digits present (e.g., no zeros).
+
+## Code Implementation
+
+<Tabs>
+  <TabItem value="Python" label="Python" default>
+  <SolutionAuthor name="@iamanolive"/>
+  ```py
+  class Solution:
+
+  	def fascinating(self, n):
+		m2 = n * 2
+		m3 = n * 3
+		num = str(n) + str(m2) + str(m3)
+		num = "".join(sorted(num))
+		zero_count = num.count("0")
+		if (num.find("123456789") == -1):
+			return False
+		elif (len(num) - zero_count > 9):
+			return False
+		else: 
+			return True
+	```
+
+  </TabItem>
+  <TabItem value="C++" label="C++">
+  <SolutionAuthor name="@iamanolive"/>
+
+  ```cpp
+  class Solution {
+  public:
+  	bool fascinating(int n) {
+	  int m2 = n * 2;
+	  int m3 = n * 3;
+	  string num = to_string(n) + to_string(m2) + to_string(m3);
+	  sort(num.begin(), num.end());
+	  if (num.find("123456789") == string::npos)
+	    return false;
+	  else if (num.length() - num.find("123456789") > 9)
+	    return false;
+	  else return true;
+	}
+};
+```
+
+  </TabItem>  
+</Tabs>
+
+
+## Example Walkthrough
+
+For N = 192:
+1. Original number: 192
+2. Multiply by 2: 192 × 2 = 384
+3. Multiply by 3: 192 × 3 = 576
+4. Concatenate: "192" + "384" + "576" = "192384576"
+5. Check if the concatenated string contains all digits from 1 to 9 exactly once: "192384576" contains each digit from 1 to 9 exactly once.
+
+Therefore, 192 is a fascinating number.
+
+## Solution Logic:
+
+1. Compute the Products: Multiply the number N by 2 and 3 to get two new numbers.
+2. Concatenate the Results: Convert the original number and the two products to strings and concatenate them.
+3. Sort and Check Digits: Sort the concatenated string and check if it contains the sequence "123456789" exactly once.
+4. Verify Length: Ensure there are no extra digits (like zero or repetitions). The total length of digits should be exactly 9, excluding any zeros.
+
+## Time Complexity
+
+The time complexity is $O(1)$ because the operations involve a fixed number of steps regardless of the size of N:
+
+* Multiplication and string concatenation are constant time operations.
+* Sorting a string of fixed length (at most 9 characters) is a constant time operation.
+* Checking for the sequence "123456789" in a fixed-length string is also a constant time operation.
+
+## Space Complexity
+
+The space complexity is $O(1)$ as well since the operations use a constant amount of extra space for storing the products and concatenated strings.
+
+## References
+
+- **LeetCode Problem:** [Geeks for Geeks Problem](https://www.geeksforgeeks.org/problems/fascinating-number3751/1?page=1&difficulty=School&sortBy=difficulty)
+- **Solution Link:** [Fascinating Number on Geeks for Geeks](https://www.geeksforgeeks.org/problems/fascinating-number3751/1?page=1&difficulty=School&sortBy=difficulty)
+- **Authors LeetCode Profile:** [Anoushka](https://www.geeksforgeeks.org/user/iamanolive/)