CODEWITHSUNDEEP
java
Breon Thibodeaux
Breon Thibodeaux

Reputation: 93

Project Euler 2 in Java

public class Euler2 {
    public static void main(String[] args) {
        int Num1 = 0;
        int Num2 = 1;
        int sum = 0;

        do
        {
            sum = Num1 + Num2;
            Num1 = Num2;
            Num2 = sum;

            if (Num2 % 2 == 0)
                sum = sum + Num2;
        }
        while (Num2 < 4000000);

        System.out.println(sum);
    }
}

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

I don't feel like I coded it wrong but the answer I'm getting is 5702887 and I know it should be 4613732.

Upvotes: 3

Views: 22620

Answers (10)

Uddhav P. Gautam
Uddhav P. Gautam

Reputation: 7626

public class FibonacciUpto4Million {
    public static void main(String[] args) {
        int a=1, b=2;
        int sum = 0;
        while(b <= 4000000) {
            //swap two variables
            a = a+b;
            b = a-b;
            a = a-b;

            if(a%2 == 0) {
                sum = sum + a;
            }

            //make b = a+b;
            b = a+b;
        }
        if(b % 2 == 0 && b <= 30) {
            sum = sum + b;
        }
        System.out.println(sum); //4613732
    }
}

Upvotes: 0

spydon
spydon

Reputation: 11522

public class Euler {
   public static void main(String[] args) {    
    int num1 = 0;
    int num2 = 1;
    int temp = 0;
    int sum = 0;

    do {
        if (num2 % 2 == 0) {
            sum = sum + num2;
        }
        temp = num1 + num2;
        num1 = num2;
        num2 = temp;
    } while (num2 < 4000000);

    System.out.println(sum);
  }
}

You messed up the sum by assigning it twice on each iteration where num2 is even. In this solution we use a temporary variable to store the next fibonacci number.

Solution = 4613732

Upvotes: 6

Dhaval Mistry
Dhaval Mistry

Reputation: 53

This might help you...

#include<stdio.h>
int  main()
{
    int i,a = 0,b = 1,temp = 0,sum = 0;
    while(temp < 4000000)
    {
        temp = a + b;
        printf("%d\n",temp);
        a = b;
        b = temp;
        if(temp % 2 == 0)
        {
            sum = sum + temp;
        }
    }
    printf("The sum is :- %d\n", sum);
    return 0;
}

Upvotes: 0

Theja Mitta
Theja Mitta

Reputation: 1

This should work:

public static void main(String[] args)
{
    int n1=0;
    int n2=1; 
    int n3=0; 
    int count=10000; 
    int limit=4000000; 
    int sum=0;
    for(int i=1;(i<=count && n3<=limit); i++)
    {
        n3=n1+n2;
        if(n3%2==0){
            sum = sum+n3;
            System.out.println(sum);
        }
        n1=n2;
        n2=n3;
    }
}

Upvotes: -1

anji_rajesh
anji_rajesh

Reputation: 369

public void execute() {
        int total = 1;
        int toBeAdded = 1;
        int limit = 4000000;
        int totalSum = 0;
        int temp = 0;
        while (total <= limit) {
            if (total % 2 == 0) {
                totalSum = totalSum + total;
            }
            temp = toBeAdded;
            toBeAdded = total;
            total = toBeAdded + temp;
        }
    }

Upvotes: 1

ROMANIA_engineer
ROMANIA_engineer

Reputation: 56666

Another solution, using:

  • while instead of do-while
  • bits operation instead of %

  • only 2 variables to keep the effective values (no aux):

    public static void main(String[] args) {
    int sum = 0 ;
    int x1 = 1;
    int x2 = 2;
    while ( x1 < 4000000 ) {
        if ( (x1 & 1) == 0 ){    // x % 2 == 0
            sum += x1;
        }
        x2=x1+x2;                // x2 = sum
        x1=x2-x1;                // x1 = the old value of x2
    }
    System.out.println(sum);
}

Upvotes: 1

Om Shankar
Om Shankar

Reputation: 8069

JavaScript: 

function printSumOfEvenFiboNumbersWithin (limit) {
    var current = 2, prev = 1, next, sum = 0;
    do {
        next = current + prev;
        prev = current;
        current = next;
        sum += prev % 2 == 0 ? prev : 0;
    } while (prev < limit);

    console.log(sum);
}

printSumOfEvenFiboNumbersWithin(4000000); // 4613732

Upvotes: -2

Doro
Doro

Reputation: 671

I just made it and I can only tell you that you need an if(... % 2 == 0){} and only sum up the even numbers.... I hope it helps you.

Upvotes: 0

musical_coder
musical_coder

Reputation: 3896

Here are some hints (and not a complete answer since this appears to be homework):

  • When doing Fibonacci, you need to provide the first two terms as 1 and 2, not 0 and 1 as you are now.
  • The if (Num2 % 2 == 0) means that, as user2573153 pointed out, the value of sum is getting doubled everytime Num2 is even. But this isn't how Fibonacci works. I can see that you're trying to continuously sum up the even terms by using that if statement. So how can you do that without messing up sum? (Hint: store up the even numbers somewhere else).

Upvotes: 0

user2573153
user2573153

Reputation: 254

I'm not sure what the program is supposed to do but part of the problem may be that you are assigning num2 to the value of sum before your if statement, making the inside of that if statement equivalent to sum = sum + sum;

On another note it is bad practice to capitalize the names of your local variables. Good luck!

Upvotes: 0

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