Solution to the Project Euler problem #1 - For the multigrad blog (entry 4)

euler1_s4.c

#include <stdio.h>

unsigned int x = 0, state = 0;

unsigned int NumberIt()
{
    /* Create a persistant variable x and initialize it to 0 */
    switch (state) {
        /* case 0: Replaced by default*/
        case 3:
        case 6:
            x += 3;
            break;
        case 1:
        case 5:
            x += 2;
            break;
        case 2:
        case 4:
            x += 1;
            break;
        default:
            state = 0;
            x += 3;
    }
    state++;
    return x;
}

int main()
{
    unsigned int lResult, lTmpValue, lLoop;
    for (lLoop = 0; lLoop <= 100000; lLoop++) {
        lResult = 0;
        while (1) {
            lTmpValue = NumberIt();
            if (lTmpValue >= 1000) {
                break;
            }
            lResult += lTmpValue;
            x = x - 1000;
            state = 0;
        }
    }
    printf("Result: %u\n", lResult);
    return 0;
}