Question

我正在尝试对哈希表程序的给定键执行一些按位操作。我想弄清楚的方法是折叠，中间正方形，截断和基数。我不希望任何人给我直接的答案，但帮助发送给我正确的方向。我找不到任何涉及此的通信或帮助，或任何可能有帮助的算法。我有一个按位程序，它显示了二进制数的一些操作，例如shift，XOR，OR，AND＆lt;等等。我不理解的是如何只选择32位二进制数的一部分，例如在中间正方形中，您将选择中间的四位，并仅使用操作中的那些。我尝试了几件事，但以下是我最终的结果。我认为中间广场的作品（虽然不确定），但似乎只适用于大整数。折叠和截断肯定不起作用。我甚至没有尝试过基数法。任何帮助，指导或向我推荐最有用的文档都会很棒。

int location = 0;

    if(hFunction == FOLDING){
        location = (key & 0xff000000) >> 2;
        location = location + ((key & 0x00ff0000) >> 2);
        location = location + ((key & 0x0000ff00) >> 2);
        location = location + ((key & 0x000000ff) >> 2);
        cout << "\n" << location << "\n";   // for debuggin
    }
    else if(hFunction == MIDSQUARE){
        location = ((key * key) & 0x00ffff00) >> 2;
        cout << "\n" << location << "\n";   // for debuggin
    }
    else if(hFunction == TRUNCATION){
        location = (key & 0x000ffff0) << 1;
        cout << "\n" << location << "\n";   // for debugging
    }
    else if(hFunction == RADIX){
        return(0);
    }

    // Divsion Method
    location %= tableSize;
    keys++;

    return(location);

编辑（修订）：好的，这是我做的一些修改。我不知道这些是否正确，但让我知道什么可以改变，更好地优化，并且是完全错误的。我得到了所有四种方法的输出，但不管是否可以，我还不知道。我没有彻底检查每一个。

修订后的代码：

int location = 0;

    // splits key and adds the sections together - discards remainder
    if(hFunction == FOLDING){
        while (key != 0){
            location = location + key % 100;
            key = key / 100;
        }
        //cout << location << "\n";         // for debugging
    }
    // squares the key and then shifts right 2 spaces
    else if(hFunction == MIDSQUARE){
        location = ((key * key) & 0x00ffff00) << 2;
        //cout << location << "\n";         // for debugging
    }
    // mods the key by 100, then divides by 10, splitting it into different digits, 
    // then adds those digits together
    else if(hFunction == TRUNCATION){
        while (key != 0){
            location = location + key % 100;
            key = key / 10;
        }
        //cout << location << "\n";         // for debugging
    }
    // converts the key to a character array while also taking all digits of the key and 
    // multiplying them by base 5, then converts back to an integer
    else if(hFunction == RADIX){
        char buffer[33];
        _itoa_s(key, buffer, 5);
        //cout << key;                      // for debugging
        //system("pause");                  // for debugging
        location = atoi(buffer);
        //cout << location << "\n";         // for debugging
    }

    // Divsion Method
    location %= tableSize;
    keys++;                                 // counts the keys per hash table

    return(location);

C ++在整数上的按位运算，例如Mid-Square，Folding和Truncation

0 个答案: