一屏样式布局

<style>
body,p{margin: 0;}
body,html,.parent{height: 100%;}
.parent{
    display: flex;
    flex-direction: column;//关键
}
.top,.bottom{
    height: 50px;
}
.middle{
    display: flex;
    flex: 1;//关键
}
.left{
    width: 100px;
    margin-right: 20px;
}
.right{
    flex: 1;
    overflow: auto;
}
.right-in{
    height: 1000px;
}
</style>

<div class="parent" id="parent" style="background-color: lightgrey;">
    <div class="top" style="background-color: lightblue;">
        <p>top</p>
    </div> 
    <div class="middle" style="background-color: pink;">
        <div class="left" style="background-color: orange;">
            <p>left</p>
        </div>     
        <div class="right" style="background-color: lightsalmon;">
            <div class="right-in">
                <p>right</p>
            </div>            
        </div>                    
    </div>              
    <div class="bottom" style="background-color: lightgreen;">
        <p>bottom</p>
    </div>        
</div>