Align list items with variable height to bottom ul

Question

I'd like to align a series of li items to the bottom of their parent, the ul. One of the tricky parts is: the li items require a float: left as well as the items being variable in height and width. Is there a way to achieve this without using a "hacky" method?

Here's my current code:

ul {
  width: 1000px;
  height: 400px;
  float: left;
  vertical-align: bottom; /* doesn't influence the list items because of the float: left. i thought i'd put it here anyways */
}

ul li {
  float: left;
  display: inline-block;
}

ul li figure {
  /* determines the width & height of the list item */
  margin: 0; padding: 0;
  width: 150px;
  height: 150px;
  background: red;
}

ul li:nth-child(2n) figure {
  width: 300px;
  height: 300px;
}

<ul>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
</ul>

NOTE: The width of the ul's width is variable and my design requires there to be no gap between the list items. This is what I'm looking to achieve:

Answer 1

float is not compatible with vertical alignement.

• inline-block & vertical-align does :

ul {
  width: 1000px;
  height: 400px;
  float: left;
}

ul li {
  /*float: left;*/
  display: inline-block;
  vertical-align:bottom
}

ul li figure {
  /* determines the width & height of the list item */
  margin: 0; padding: 0;
  width: 150px;
  height: 150px;
  background: red;
}

ul li:nth-child(2n) figure {
  width: 300px;
  height: 300px;
}

<ul>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
</ul>

• display:flex & align-items does :

ul {
  width: 1000px;
  height: 400px;
  display:flex;
  align-items:flex-end;
  
}

ul li {
display:block;
float:right;
/* whatevever float or display will be overide by flex model */
margin:1px; /* is efficent */
}

ul li figure {
  /* determines the width & height of the list item */
  margin: 0; padding: 0;
  width: 150px;
  height: 150px;
  background: red;
}

ul li:nth-child(2n) figure {
  width: 300px;
  height: 300px;
}

<ul>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
</ul>

• display:grid

* {margin:0;padding:0;}
ul {
  width: 1000px;
  height: 400px;
  float: left;
  display:grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 0));
  grid-auto-flow: dense;
  grid-auto-rows: minmax(150px, 300px);
  grid-gap: 1px;/* whatever */
  align-items: end;/* or align-self on children */
}

ul li {
  display:block;
  /* align-self: end; */
}
ul li:nth-child(2n) {
  grid-column: span 2;}

ul li figure {
  margin: 0; padding: 0;
  width: 150px;
  height: 150px;
  background: red;
}

ul li:nth-child(2n) figure {
  width: 300px;
  height: 300px;
}

<ul>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
</ul>

• display:table of course

Answer 2

See snippet, note that the fixed width on the ul means an even distribution of the li with table-cell, so you may need to work on that in regards to the "gaps" between the li. As you didn't specify how that is supposed to look I didn't try to solve it in any specific way.

I think this is the way to go to get a bottom align.

ul {
  height: 400px;
  float: left;
  display: table;
  list-style: none;
}

ul li {
  display: table-cell;
  vertical-align: bottom;
  margin: 0;
  padding: 0;
}

ul li figure {
  /* determines the width & height of the list item */
  margin: 0; 
 padding: 0;
  width: 150px;
  height: 150px;
  background: red;
  display: inline-block;
}

ul li:nth-child(2n) figure {
  width: 300px;
  height: 300px;
}

<ul>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
  <li>
    <figure>
      <img />
    </figure>
  </li>
</ul>