学步园

用1,2,3,...,9组成3个三位数abc，def和ghi，每个数字恰好使用一次，要求abc:def:ghi=1:2:3。输出所有解。

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

int a[9] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
char found = 0;
void swap(int *a, int *b)
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}
void getNum(int begin, int n)
{
    int i, first, second, third;
    if (found)
    {
        return;
    }
    if (begin >= n)
    {
        first = a[0]*100+a[1]*10+a[2];
        second = a[3]*100+a[4]*10+a[5];
        third = a[6]*100+a[7]*10+a[8];
        if ((2*first == second)
            && (3*first == third))
        {
            printf("first = %d\n", first);
            printf("second = %d\n", second);
            printf("third = %d\n", third);
            found = 1;
            return;
        }
    }
    else
    {
        for (i = begin; i < n; i++)
        {
            swap(&a[begin], &a[i]);
            getNum(begin+1, n);
            swap(&a[begin], &a[i]);
        }
    }
}

int main()
{
    getNum(0, 9);

    return 0;
}