c - 减少操作次数

Question

我有一个函数可以切换每个十六进制数字的第 0 位和第 3 位，但它使用 26 次操作。我只想将其减少到 1 到 25 次操作。仅使用位运算! ~ & ^ | + << >>.

int swap30(int x) {
    int m = 0b10001000 << 24;
    int m1 = 0b10001000 << 16;
    int m2 = 0b10001000 << 8;
    int m3 = 0b10001000;
    int mask1 = m | m1 | m2 | m3;

    int z = 0b01100110 << 24;
    int z1 = 0b01100110 << 16;
    int z2 = 0b01100110 << 8;
    int z3 = 0b01100110;
    int mask2 = z | z1 | z2 | z3;

    int y = 0b00010001 << 24;
    int y1 = 0b00010001 << 16;
    int y2 = 0b00010001 << 8;
    int y3 = 0b00010001;
    int mask3 = y | y1 | y2 | y3;

    int three = x & mask1;
    int stable = x & mask2;
    int one = x & mask3;
    int final2 = ((three >> 3) & mask3) | stable | (one << 3);
    return final2;
}

Answer 1

return (x & 0x66666666) | ((x >> 3) & 0x11111111) | ((x & 0x11111111) << 3);