力卉编程 | C语言算法 | 用11x11方式计算超长乘法

我们都知道 11 * 11 = 121，超长计算还是按照这种规则计算。
把前32位的计算了，再计算后面的32位，最后通过移位把正确的值放入对应的长整形中。

程序设计的思路就是简单的叠加

注意： unsigned long long u1 * unsigned long long u2 最后的结果是两个unsigned long long数据哦。

实例代码：

void ull_x_ull(unsigned long long dbP1, unsigned long long dbP2)
{
    unsigned long long dbBuf1[2];
    unsigned long long dbBuf2[2];
    unsigned long long dbRes[2];
    unsigned long long dbTmp[2];
    unsigned long long dbTmpRes;

    //dbP1 = 8589934592+1;
    //dbP2 = 8589934592+1;

    printf("sizeof(longlong) = %d\n", sizeof(dbBuf1));


    printf("\ndbP1, dbP2 = %llx , %llx\n", dbP1, dbP2);
    printf("dbP1, dbP2 = %llu , %llu\n", dbP1, dbP2);

    dbBuf1[0] = (dbP1 & 0xFFFFFFFF00000000)>>32;
    dbBuf1[1] = dbP1 & 0x00000000FFFFFFFF;

    printf("dbBuf1 = %llx - %llx\n", dbBuf1[0], dbBuf1[1]);

    dbBuf2[0] = (dbP2 & 0xFFFFFFFF00000000)>>32;
    dbBuf2[1] = dbP2 & 0x00000000FFFFFFFF;

    printf("dbBuf2 = %llx - %llx\n", dbBuf2[0], dbBuf2[1]);

    //low *
    dbRes[1] = dbBuf1[1] * dbBuf2[1];//result of low 32 bits
    printf("dbRes[1] = %llx\n", dbRes[1]);

    dbTmp[0] = dbBuf1[0] * dbBuf2[1];
    dbTmp[1] = dbBuf1[1] * dbBuf2[0];

    printf("dbTmp[0], dbTmp[1] = %llx , %llx\n", dbTmp[0], dbTmp[1]);

    dbTmpRes = dbTmp[0] + dbTmp[1];//result of low 32 bits * high 32 bits
    printf("dbTmpRes = %llx\n", dbTmpRes);

    dbRes[1] = dbRes[1] + ((dbTmpRes & 0x00000000FFFFFFFF)<<32);
    //high calc
    dbRes[0] = dbBuf1[0] * dbBuf2[0];//result of high 32 bits
    printf("dbRes[0] = %llx\n", dbRes[0]);

    dbRes[0] = dbRes[0] + ((dbTmpRes & 0xFFFFFFFF00000000)>>32);//result of all + high 32 bits

    printf("dbRes[0], dbRes[1] = %llx - %llx\n", dbRes[0], dbRes[1]);
    printf("dbRes[0], dbRes[1] = %llu - %llu\n", dbRes[0], dbRes[1]);
    
    printf("Result X: %llx%016llx\n", dbRes[0], dbRes[1]);
    printf("Result L: %llu-%llu\n", dbRes[0], dbRes[1]);
}
int main(int argc)
{
  ull_x_ull(8589934592+1, 8589934592+1);
}

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