紫书 习题2-6 排列

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

int main()
{
    int i, count = 0, j, k, a[10], c;//用i表示abc,j表示def,k表示ghi
    memset(a, 0, sizeof(a));//初始化数组，全部为零
    for ( i=123; i<=329; i++ )
    {
        j = i*2;
        k = i*3;
        a[i/100] = a[i/10%10] = a[i%10] = 1;//分别标记出现过的数字
        a[j/100] = a[j/10%10] = a[j%10] = 1;
        a[k/100] = a[k/10%10] = a[k%10] = 1;
        for ( c=0; c<10; c++ )
            count += a[c];
        if ( count == 9 ) //只有1到9每个数字被标记结果才为9
            printf("%d\n%d\n%d\n", i, j, k);
        count = 0;
        memset(a, 0, sizeof(a));
    }

    return 0;
}