最后一个右对齐-使用margin-left
.box{
display: flex;
}
.child{
width: 100px;
height: 100px;
margin: 50px;
background-color: pink;
}
.child:last-child{
background-color: purple;
margin-left: auto;
}
<div class="box">
<div class="child"></div>
<div class="child"></div>
<div class="child"></div>
<div class="child"></div>
<div class="child"></div>
</div>
