Added solution to Problem 14

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2020-06-16 13:36:27 -04:00
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//ProjectEulerRust/src/Problems/Problems14.rs
//Matthew Ellison
// Created: 06-16-20
//Modified: 06-16-20
//Work out the first ten digits of the sum of the following one-hundred 50-digit numbers
/*
The following iterative sequence is defined for the set of positive integers:
n → n/2 (n is even)
n → 3n + 1 (n is odd)
Which starting number, under one million, produces the longest chain?
*/
//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/RustClasses
/*
Copyright (C) 2020 Matthew Ellison
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
extern crate myClasses;
use crate::Problems::Answer::Answer;
pub fn getDescription() -> String{
"Which starting number, under one million, produces the longest chain using the itterative sequence?".to_string()
}
pub fn solve() -> Answer{
let MAX_NUM = 1_000_000_i64;
//This is the length of the longest chain
let mut maxLength = 0i64;
//This is the starting number of the longest chain
let mut maxNum = 0i64;
//Start the timer
let mut timer = myClasses::Stopwatch::Stopwatch::new();
timer.start();
//Loop through all numbers less than MAX_NUM and check them against the series
for currentNum in 1i64..MAX_NUM{
let currentLength = checkSeries(currentNum);
//If the current number has a longer series than the max then the current becomes the max
if(currentLength > maxLength){
maxLength = currentLength;
maxNum = currentNum;
}
}
//Stop the timer
timer.stop();
//Return the results
return Answer::new(format!("The number {} produced a chain of {} steps", maxNum, maxLength), timer.getString());
}
fn checkSeries(startNum: i64) -> i64{
let mut num = startNum;
//Start at 1 because you need to count the starting number
let mut length = 1i64;
//Follow the series, adding 1 for each step you take
while(num > 1){
if((num % 2) == 0){
num /= 2;
}
else{
num = (3 * num) + 1;
}
length += 1;
}
//Return the length of the series
return length;
}
/* Results:
The number 837799 produced a chain of 525 steps
It took 98.253 milliseconds to solve this problem
*/