display:flex布局，自动适应屏幕高度100%

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    html,body{
      height: 100%;
    }
    .box{
      display: flex;
      height: 100%;
      background-color: pink;
    }
    .content{
      height: 100%;
    }
  </style>
</head>
<body>
  <div class="box">
    <div class="content">11</div>
    <div></div>
  </div>
</body>
</html>

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