数学趣题——哥德巴赫猜想的近似证明

一、分析

    可在较小范围内使用枚举法，验证每一个偶数是否能表示成为两个素数的和。

二、源码

#include <string.h>
#include <stdio.h>

int IsGoldbach(int a);
int TestifyGB_Guess(int low, int high);
int IsPrime(int i);

int main()
{
    printf("Test 1-100 is Goldbach Guess\n");
    if (TestifyGB_Guess(1, 100))
        printf("in 1-100 guess is right\n");
    else
        printf("guess is wrong\n");
    return 0;
}

int TestifyGB_Guess(int low, int high)
{
    int i, j = 0;
    int flag = 0;

    for (i = low; i <= high; ++i)
    {
        if (i % 2 == 0 && i > 2)
        {
            if (IsGoldbach(i))
            {
                j++;
                if (j == 5)
                {
                    printf("\n");
                    j = 0;
                }
            }
            else
            {
                flag = 1;
                break;
            }
        }
    }

    if (flag == 0)
        return 1;
    else
        return 0;
}

int IsGoldbach(int a)
{
    int i, flag = 0;
    for (i = 1; i <= a / 2; ++i)
    {
        if (IsPrime(i) && IsPrime(a - i))
        {
            flag = 1;
            printf("%d=%d+%d ", a, i, a-i);
            break;
        }
    }

    if (flag == 1)
        return 1;
    else
        return 0;
}

int IsPrime(int i)
{
    int n, flag = 1;
    if (1 == i)
        flag = 0;

    for (n=2; n<i; n++)
    {
        if (i%n == 0)
        {
            flag = 0;
            break;
        }
    }

    if (flag == 1)
        return 1;
    else
        return 0;
}