Implementation of CSS fixed layout on both sides and adaptive layout in the middle

<style type="text/css">
    .wrap {background: #eee; padding: 20px; }
    p {margin: 0; }
    .left {width: 200px; height: 200px; float: left; background: coral; }
    .right {width: 200px; height: 200px; float: right; background: lightblue; }
    .middle {margin: 0 200px; background: lightpink; }
</style>

<div class="wrap">
    <p class="left">I am on the left</p>
    <p class="right">I am on the right</p>
    <p class="middle">I was last in line, but I ran to the middle</p>
</div> 

<style type="text/css">
    .wrap {background: #eee; padding: 20px; }
    p {margin: 0; }
    .left {width: 200px; height: 200px; float: left; background: coral; margin-left: -100%;}
    .right {width: 200px; height: 200px; float: left; background: lightblue; margin-left: -200px;}
    .middle {width: 100%; height: 200px; float: left; background: lightpink; }
    span{
        display: inline-block;
        margin: 0 200px;
    }
</style>

<div class="wrap">
    <p class="middle">
        <span class="inner">
            I'm in the middle 
    </p>
    <p class="left">I am on the left</p>
    <p class="right">I am on the right</p>
</div> 

<style type="text/css">
    .wrap {background: #eee; position: relative;}
    p {margin: 0; }
    .left {width: 200px; height: 200px; background: coral; position: absolute;left: 0; top: 0;}
    .right {width: 200px; height: 200px; background: lightblue; position: absolute; right: 0; top: 0;}
    .middle {height: 200px; background: lightpink; margin: 0 200px;}
</style>

<div class="wrap">
    <p class="middle">I am in the middle, I use margin to offset the space occupied by the two positioned elements on the left and right</p>
    <p class="left">I am on the left, I am a positioned element</p>
    <p class="right">I am on the right, I am a positioned element</p>
</div> 

<style type="text/css">
    .wrap {background: #eee; display: flex}
    p {margin: 0; }
    .left {width: 200px; height: 200px; background: coral; }
    .right {width: 200px; height: 200px; background: lightblue; }
    .middle {height: 200px; background: lightpink; flex: 1;}
</style>

<div class="wrap">
    <p class="left">I am on the left</p>
    <p class="middle">I am in the middle, flex: 1 automatically occupies the remaining space</p>
    <p class="right">I am on the right</p>
</div>