diff --git a/problem03.rb b/problem03.rb index e69de29..52210dc 100644 --- a/problem03.rb +++ b/problem03.rb @@ -0,0 +1,27 @@ +#Project Euler, Problem #3 +#What is the largest prime factor of the number 600851475143? + +def primeTest testnum + #"For each number between 2 and testnum-1, we will test if number%a = 0 and stop when it does" + (2..(testnum-1)).each {|a| return false if testnum % a==0} + return true +end + + +num = 600851475143 +#sumtest is the sum of the 2 prime factors, once we have both we can stop +lastfactor = 1 +curr = 2 +sumtest = 1 + +#while loop to test +#every number must have 2 prime factors + while sumtest < num + if num % curr == 0 && primeTest(curr) + lastfactor = curr + sumtest*=curr + end + curr+=1 + end +# lastfactor will always have largest num last so we can just print it +puts "num is #{lastfactor}" \ No newline at end of file diff --git a/problem05.rb b/problem05.rb index e69de29..7c39e06 100644 --- a/problem05.rb +++ b/problem05.rb @@ -0,0 +1,22 @@ +#Project Euler, PROBLEM #5 +#2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. +#What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20? + +def divisorTest testnum + #"We check if the input number is dividable by all numbers encased in 11-20" + (11..20).each { |x| return false if testnum % x != 0 } + return true +end + +ceil = 20 +found = false + +while found == false + #tests if ceil works, if it does the loop will end and the console puts the number that works. + if divisorTest(ceil) + found=true + puts "#{ceil} is divisible by every number between 1 and 20." + end + #increments by 20 and starts with 20 inorder to save time, since checking every number would prove unoptimized + ceil+=20 +end \ No newline at end of file diff --git a/problem08.rb b/problem08.rb index e69de29..ab1eab4 100644 --- a/problem08.rb +++ b/problem08.rb @@ -0,0 +1,19 @@ +#Find the greatest product of five consecutive digits in the 1000-digit number. (used below) +number = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450" +#the number is in string format since a string is just an array of chars so its easy to use arrays + +loop = 0; +hiscore = 0; +currscore = 0; + +#length-4 to stop invalid memory to mess with things +while loop < number.length-4 + #to_i makes the character an integer + currscore = number[loop].to_i*number[loop+1].to_i*number[loop+2].to_i*number[loop+3].to_i*number[loop+4].to_i + if currscore > hiscore + hiscore = currscore + end + loop+=1 +end + +puts "highscore is #{hiscore}"