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October 14, 2017 07:04
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Project Euler Problem 14 - Longest Collatz Sequence in Java
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package com.javamultiplex.projecteuler; | |
import java.util.ArrayList; | |
import java.util.List; | |
/** | |
* | |
* @author Rohit Agarwal | |
* @category Project Euler Problems | |
* @Problem 14 - Longest Collatz Sequence. | |
* | |
*/ | |
public class Problem14 { | |
public static void main(String[] args) { | |
int limit = 1000000; // Limit is one million | |
int size = 0, max = 1, j = 0; | |
for (int i = 2; i < limit; i++) { | |
size = getChainSize(i); | |
if (size > max) { | |
max = size; | |
j = i; | |
} | |
} | |
System.out.println("Starting number, under one million, produces the longest chain is : " + j); | |
} | |
private static int getChainSize(int n) { | |
long num = n; | |
List<Long> list = new ArrayList<>(); | |
int size = 0; | |
while (num != 1) { | |
list.add(num); | |
/* | |
* As per Collatz sequence condition, if num is even then num=num/2 | |
* else num=3*num+1 | |
*/ | |
if (num % 2 == 0) { | |
num = num / 2; | |
} else { | |
num = 3 * num + 1; | |
} | |
} | |
size = list.size(); | |
return size; | |
} | |
} |
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