Challenge: Simple And Easy Number Division

Question

Consider positive integers that are divisible by 7, and are also divisible by 7 when you reverse the digits. For instance, 259 counts, because 952 is also divisible by 7. The list of all such numbers between 0 and 10^3 is:
7 70 77 161 168 252 259 343 434 525 595 616 686 700 707 770 777 861 868 952 959
The sum of these numbers is 10,787.
Find the sum of all such numbers betwen 0 and 10^11.
Make your program work for an upper limit of 10^N for any N, and be able to efficiently handle N's much larger than 11.

Answer 1

/* for those who don't understand the challenge 👇

find sum of numbers between 0 and 10^n where n is a positive integer(obviously) , numbers must be of form 7x and its reverse of form 7y , where x,y belongs to set of natural number

//hope i explained well , & it makes sense 2 u ☺
*/

⬜🌹🌹🌹🌹🌹⬜
🌹⬜⬜⬜⬜⬜⬜
🌹⬜⬜⬜⬜⬜⬜
🌹⬜⬜⬜🌹🌹🌹 //here is my try 👇 (& yes , thats v. easy when u understand what is the question )
🌹⬜⬜⬜⬜⬜🌹
🌹⬜⬜⬜⬜⬜🌹
⬜🌹🌹🌹🌹🌹⬜

https://code.sololearn.com/cx98ungMZe6w/?ref=app

Answer 2

@gawen , in mine code , time limit exceeded for 10^11 ,

//but , i have made it to take least time , u can see the code ... if some improvement can be done ... then tell

//it will work for 10^3

Answer 3

@Gaurav I mean you have first take number which reverse is also divisible by 7 and then you have to sum that numbers and print it the range should be satisfied any user input

Answer 4

this is my try check it guys😊😊
https://code.sololearn.com/cHGFYya05luZ/?ref=app

Answer 5

Gawen ur question is not too clear

Answer 6

Gawen, my try
https://code.sololearn.com/cHN0lc429Bw1/?ref=app

Answer 7

Don't know if it works or not. You can't run it on code playground because it takes too much memory. Try to run it on a different compiler.
https://code.sololearn.com/c1e37LU4Sg40/?ref=app

Answer 8

I made one that I think can do 10^11 but the memory limit exceeded.

Answer 9

Gawen, your code is amazing 👍
Here's my try:
https://code.sololearn.com/cyEfkvQc12Cy/?ref=app

Answer 10

gawEINSTEINasy series! 😱😱

Answer 11

🌾🌾

https://code.sololearn.com/cSazcsf7AdXj/?ref=app

Answer 12

https://code.sololearn.com/cZVIXGQTlI9u/?ref=app

Answer 13

Here is my try
https://code.sololearn.com/cKO3o0h4HsP6/?ref=app

Answer 14

Here is my try.
My code isn't efficient to solve N=11 case in CodePlayground..
https://code.sololearn.com/cGv9UZZkqnCm/?ref=app

Answer 15

java
https://code.sololearn.com/cz8WAQEeWGNj/?ref=app

Answer 16

another solution in python:

https://code.sololearn.com/cqeVrlCQphKu/#py

Answer 17

my python solution:

https://code.sololearn.com/cVM1qTEnK6Y9/#py

Answer 18

https://code.sololearn.com/c6JrqYEeT8eA/?ref=app

Will work till 10^1000000 but not completed yet.

I just need 2-3 more lines to write which I don't know 😥