css父元素高度自适应

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Height Auto Adjust</title>
    <style>
        .parent {
            display: flex;
            flex-direction: column;
            border: 1px solid #000;
        }
        .child {
            flex-grow: 1;
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
    <div class="parent">
        <div class="child">Content 1</div>
        <div class="child">Content 2</div>
    </div>
</body>
</html>