甚至C中的斐波那契数，难题

Question

Problem:

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've looked up another way to do this, but I am confused as to why my method does not work. I've included the code as well as my written algorithmic process below it. No matter which span of iterations of the value k I choose (4000000 or 10), I always receive the same answer: 4200784. Thanks for the help.

#include <stdio.h>

int main()
{
long int sum;
sum = 0;
long int i;
i = 1;
long int j;
j = 2;
long int k;

while(k<4000000)
{   
    k = i + j;
    if(k%2==0)
        sum +=k;
    i = j;
    j = k;

}
printf("%d",sum);
return 0;
}

//Step 0//For the initial conditions [i][j]=[1][2]
//Step 1//Find the value of i + j.
//Step 2//Find out if the solution is even by dividing by modulus 2.
//Step 3//If even, add the solution to the sum.
//Step 4//Replace the value of i with j, and replace the value of j with the new sum.
//Repeat Steps 1-4 while i + j < 4,000,000
//1, 2, 3, 5, 8, 13, 21, 34

Answer 1

I believe your looking for

sum += k;

not

k+=sum;

You should also fix this and place it inside your while loop

k = i + j;

Note: you should also initialize sum to 0

Answer 2

You never initialize your 'k' variable. On that first 'while' test, you have an undefined value for 'k', so all bets are off.