连接两个数字的位的代码不起作用 [英] Code to concatenate two numbers' bits not working

问题描述

任务是连接两个给定数字的二进制。

The task is to concat the binary of 2 given numbers.

示例：

给出 5 （ 101 ）和 3 （ 011 ），结果为 46 （ concat（101，011）= 101011 ）

Given 5 (101) and 3 (011), the result is 46 (concat(101, 011) = 101011)

到目前为止的代码：

public class Concat {
    public static void main(String[] args) {
      int t = 0;
      int k = 5;
      int x = 3;
      int i = 0;
       while (i < 3) {
           t = x % 2;
            x /= 2;
            k <<= 1;
            k |= t;
           ++i;
       }

      System.out.println(k);
    }

}

但是问题在于代码给出 101110 ，而不是 101011 。

But the problem is that the above code gives 101110, not 101011.

什么是

推荐答案

您的问题是您正在向后 中输入第二个数字的位。这是因为 x％2 是低位：

Your problem is that you're feeding the bits of the second number in backwards. That's because x%2 is the low order bit:

+---+---+---+       <110
| 1 | 0 | 1 | <-----------------+^
+---+---+---+                   |1
              +---+---+---+     |1
              | 0 | 1 | 1 | ----+0
              +---+---+---+ 011>

Cringe 尽我最大的艺术才能：-)但是，如果您已经知道它是3位宽，只需使用：

Cringe at my awesome artistic abilities :-) However, if you already know that it's 3 bits wide, just use:

public class concat {
    public static void main (String[] args) {
        int t = 0;
        int k = 5;
        int x = 3;

        k <<= 3;
        k |= x;
        // or, in one line: k = (k << 3) | x;

        System.out.println(k);
    }
}

---

就图形外观而言：

---

In terms of how that looks graphically:

                  +---+---+---+
                k:| 1 | 0 | 1 |
                  +---+---+---+
                  +---+---+---+
                x:| 0 | 1 | 1 |
                  +---+---+---+

      +---+---+---+---+---+---+
k<<=3:| 1 | 0 | 1 | 0 | 0 | 0 |
      +---+---+---+---+---+---+
                  +---+---+---+
                x:| 0 | 1 | 1 |
                  +---+---+---+

      +---+---+---+---+---+---+
 k|=3:| 1 | 0 | 1 | 0 | 1 | 1 |
      +---+---+---+---+---+---+
                    ^   ^   ^
                  +---+---+---+
                x:| 0 | 1 | 1 |
                  +---+---+---+

---

没有明显的理由一次这样做。

---

There's no apparent reason for doing it one bit at a time.

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