Question

我知道，42是所有事情的答案，但这是怎么回事42？

int x = -(~'+'|0xAB^1337); //42

Answer 1

要了解会发生什么，您应该查看此表达式中值的二进制表示。但在此之前，让我们看一下如何将字符转换为整数，以及在这里使用位运算符。

'+'字符相当于整数值43 - 您可以通过将其转换为整数或使用Convert.ToInt32('+')来检查它。

0xAB是hexadecimal literal，代表十进制值171。

这里你应该理解的最后一件事是bitwise operators：

~按位NOT - 运算符查看表达式值的二进制表示，并对其执行按位求反运算。表达式中任何1的数字在结果中变为0。表达式中任何0的数字在结果中变为1。
|按位OR - 查看两个表达式的值的二进制表示，并对它们执行按位OR运算。每当任何一个表达式的数字为1时，结果将在该数字中有1。否则，结果将在该数字中为0。
^按位异或 - 查看两个表达式的值的二进制表示，并对它们执行按位异或运算。当一个且只有一个表达式的数字为1时，结果在该数字中为1。否则，结果在该数字中为0。

现在所有表达式都看起来像-(NOT(43) OR (171 XOR 1337))。让我们转到二进制表示这些数字和操作：

                          Binary | Decimal | Comments

00000000000000000000000000101011 |      43 | '+'
11111111111111111111111111010100 |     -44 | NOT 43         // bits are inverted

00000000000000000000000010101011 |     171 | 0xAB
00000000000000000000010100111001 |    1337 | 
00000000000000000000010110010010 |    1426 | 171 XOR 1337   // different bits produce 1

11111111111111111111111111010100 |     -44 | NOT 43
00000000000000000000010110010010 |    1426 | 171 XOR 1337
11111111111111111111111111010110 |     -42 | -44 OR 1426    // 0 only if both bits are 0

00000000000000000000000000101010 |      42 | -(-42)

Try online

Answer 2

评估~'+'，它是'+' =＆gt;的ascii值的二进制非值-44
评估0xAB^1337（二进制XOR）=＆gt; 1426
评估-44|1426（二进制OR）=＆gt; -42
评估-42（算术否定）=＆gt; 42

Answer 3

好吧，让我们一步一步解码：

<div class="panel panel-default">
  <div class="panel-heading">
    <h3 class="panel-title pull-left" *ngIf="empInfo && empInfo.length > selectedEmployee">{{empInfo[selectedEmployee].LastName | uppercase}} Summary</h3>
    <div style="float: right;">
      <div class="onoffswitch">
        <input [(ngModel)]="checkboxValue" (change)="changeTime()" type="checkbox" name="onoffswitch" class="onoffswitch-checkbox" id="myonoffswitch" checked>
        <label class="onoffswitch-label" for="myonoffswitch">
          <span class="onoffswitch-inner"></span>
          <span class="onoffswitch-switch"></span>
        </label>
      </div>
    </div>
    <div class="clearfix"></div>
  </div>
  <div class="panel-body">
    <form class="form-horizontal" role="form" style="overflow-x:auto;">
      <fieldset>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> Status </label>
            <div class="col-xs-7">
              <select class="form-control" id="empStatus" [(ngModel)]="empInfo[selectedEmployee].EmpStat" name="empStatus">
                <option value="Current">Current</option>
                <option value="Terminated">Terminated</option>
              </select>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> Anniversary </label>
            <div class="col-xs-7">
              <input class='form-control' type="text" id="empAnniversary" [(ngModel)]="empInfo[selectedEmployee].Anniversary" name="empAnniversary"/>
            </div>
          </div>
         </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> Start Date </label>
            <div class="col-xs-7">
              <input class='form-control' type="text" id="empStartDate" [ngModel]="empInfo[selectedEmployee].StartDate | date: 'MM/dd/y'" name="empStartDate"/>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> Adjusted Start </label>
            <div class="col-xs-7">
              <input class='form-control' type="text" id="empAdjustedStart" [ngModel]="empInfo[selectedEmployee].AdjustedStart | date: 'MM/dd/y'" name="empAdjustedStart"/>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> STD/LTD </label>
            <div class="col-xs-7">
              <input class='form-control' type="text" id="empSTDLTD" [(ngModel)]="empInfo[selectedEmployee].STDLTD + timeVar" name="empSTDLTD"/>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-5"> Uncharged </label>
            <div class="col-xs-7">
              <input class='form-control' type="text" id="empUncharged" [(ngModel)]="empInfo[selectedEmployee].Uncharged + timeVar" name="empUncharged"/>
            </div>
          </div>
        </div>
      </fieldset>


      <fieldset>

        <h4>PTO</h4>
        <br />

        <div class="col-xs-12">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <div class="col-xs-1"></div>
            <label class="col-xs-2"> Base </label>
            <div class="col-xs-3">
              <input class='form-control' type="text" id="ptoBase" [(ngModel)]="empInfo[selectedEmployee].PTOBase + timeVar" name="ptoBase"/>
            </div>
            <div class="col-xs-6">
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-2" style="font-weight: bold;"> &#43; </label>
            <label class="col-xs-4"> Carryover </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoCarry" [(ngModel)]="empInfo[selectedEmployee].PTOCarry + timeVar" name="ptoCarry"/>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <div class="col-xs-1"></div>
            <label class="col-xs-4"> Balance </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoBalance" [(ngModel)]="empInfo[selectedEmployee].PTOBalance + timeVar" name="ptoBalance"/>
            </div>
            <div class="col-xs-1"></div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-2" style="font-weight: bold;"> &#8213; </label>
            <label class="col-xs-4"> Borrowed </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoBorrowed" [(ngModel)]="empInfo[selectedEmployee].PTOBorrowed + timeVar" name="ptoBorrowed"/>
            </div>
          </div>
          <hr style="border: solid 1px black;border-bottom:1px solid black;clear:both" />
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-1" style="font-weight: bold;"> &#8213; </label>
            <label class="col-xs-4"> Requests </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoRequests" [(ngModel)]="empInfo[selectedEmployee].PTORequests + timeVar" name="ptoRequests"/>
            </div>
            <div class="col-xs-1"></div>
          </div>
          <hr style="border: solid 1px black;border-bottom:1px solid black;clear:both" />
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-2" style="font-weight: bold;"> &#61; </label>
            <label class="col-xs-4"> Balance </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoBalance" [(ngModel)]="empInfo[selectedEmployee].PTOBalance + timeVar" name="ptoBalance"/>
            </div>
          </div>
        </div>
        <div class="col-xs-6">
          <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
            <label class="col-xs-1" style="font-weight: bold;"> &#61; </label>
            <label class="col-xs-4"> Available </label>
            <div class="col-xs-6">
              <input class='form-control' type="text" id="ptoRemaining" [(ngModel)]="empInfo[selectedEmployee].PTORemaining + timeVar" name="ptoRemaining"/>
            </div>
            <div class="col-xs-1"></div>
          </div>
        </div>
      </fieldset>


      <fieldset>

        <h4>ETO</h4>
        <br />

          <div class="col-xs-6">
            <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
              <div class="col-xs-2"></div>
              <label class="col-xs-4"> Earned </label>
              <div class="col-xs-6">
                <input class='form-control' type="text" id="etoEarned" [(ngModel)]="empInfo[selectedEmployee].ETOEarned + timeVar" name="etoEarned"/>
              </div>
            </div>
            <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
              <label class="col-xs-2"> &#8213; </label>
              <label class="col-xs-4"> Requests </label>
              <div class="col-xs-6">
                <input class="form-control" type="text" id="etoRequests" [(ngModel)]="empInfo[selectedEmployee].ETORequests + timeVar" name="etoRequests"/>
              </div>
            </div>
            <hr style="border: solid 1px black;border-bottom:1px solid black;clear:both" />
            <div class="form-group" *ngIf="empInfo && empInfo.length > selectedEmployee">
              <label class="col-xs-2"> &#61; </label>
              <label class="col-xs-4"> Available </label>
              <div class="col-xs-6">
                <input class='form-control' type="text" id="etoRemaining" [(ngModel)]="empInfo[selectedEmployee].ETORemaining + timeVar" name="etoRemaining"/>
              </div>
            </div>
          </div>
          <div class="col-xs-6"></div>

      </fieldset>
    </form>
  </div>
</div>

Answer 4

转换为十六进制提供了一种相对简单的手动二进制计算方法：

'+'的代码为0x2B，或二进制的00101011
0x2B的倒置位模式为0xFFFFFFD4
XOR ^的优先级高于OR |，因此0xAB首先与1337进行异或（1337为0x539）
XOR的结果是000010101011 ^ 010100111001 = 010110010010或0x592
0xFFFFFFD4和0x00000592的按位OR生成0xFFFFFD6
否定此项会产生0x0000002A，等于小数为42。

结果声明的说明

4 个答案: