HTML을 수정하지 않고 CSS로 3열 레이아웃을 만드는 방법은 무엇입니까?

.column-left {
  float: left;
  width: 33.333%;
}

.column-right {
  float: right;
  width: 33.333%;
}

.column-center {
  display: inline-block;
  width: 33.333%;
}

<div class="container">
  <div class="column-center">Column center</div>
  <div class="column-left">Column left</div>
  <div class="column-right">Column right</div>
</div>

.column {
  float: left;
  position: relative;
  width: 20%;
  
  /*for demo purposes only */
  background: #f2f2f2;
  border: 1px solid #e6e6e6;
  box-sizing: border-box;
}

.column-offset-1 {
  left: 20%;
}
.column-offset-2 {
  left: 40%;
}
.column-offset-3 {
  left: 60%;
}
.column-offset-4 {
  left: 80%;
}

.column-inset-1 {
  left: -20%;
}
.column-inset-2 {
  left: -40%;
}
.column-inset-3 {
  left: -60%;
}
.column-inset-4 {
  left: -80%;
}