Thread: fibonacci

  1. #1
    Registered User
    Join Date
    Apr 2017


    Hi. im trying to sum even fibonacci numbers only. ie. 0 2 2 4 6 10 16 ect.. could someone indicate where i've gone wrong.

    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    int main (void)
        int x, y;
        int second =0;
        int sum;
        printf("enter the fib number: ");
        scanf("%d", &y);
        for (x=0; x<=y; x++)
            if (x%2 ==0 )
                    sum = x+ second;
                    second =x;
        printf("%d \n", sum);
    return 0;

  2. #2
    Registered User
    Join Date
    Jun 2015
    You need to scrap that code and write a program that just prints out the fibonacci numbers. Then modify that program by adding code to sum up the even numbers.

    BTW, you should probably use long (or long long) integers since fibs get big fast. Even an unsigned 64-bit integer maxes out at the 93'rd fib.

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