Force content to fit full width after sidebar collapsed Bootstrap - twitter-bootstrap-3

Question

I'm using this updated Bootstrap sidebar collapse in my page, but here the sidebar & content have a fixed width for both divs, the main content is not taking full width after it has collapsed.
HTML:
<div class="col-md-3 col-xs-1 p-l-0 p-r-0 collapse in" id="sidebar">...</div>
<main class="col-md-9 col-xs-11 p-l-2 p-t-2">...</main>
But what I want is after the sidebar collapsed, main content should take full width.
I checked this and few other questions from stack overflow but didn't find what I want

Answer 1

Here's what needed to be done:
First I replaced the outdated col-xs with col. Then I replaced the remaining col-md-9 col-11 with col. Done!
The reason why it's working is because the first column for the sidebar is defined already. col then just fills out all of the available remaining space.
Here's the working code:
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<style>
#sidebar .list-group-item {
border-radius: 0;
background-color: #333;
color: #ccc;
border-left: 0;
border-right: 0;
border-color: #2c2c2c;
white-space: nowrap;
}
/* highlight active menu */
#sidebar .list-group-item:not(.collapsed) {
background-color: #222;
}
/* closed state */
#sidebar .list-group .list-group-item[aria-expanded="false"]::after {
content: " \f0d7";
font-family: FontAwesome;
display: inline;
text-align: right;
padding-left: 5px;
}
/* open state */
#sidebar .list-group .list-group-item[aria-expanded="true"] {
background-color: #222;
}
#sidebar .list-group .list-group-item[aria-expanded="true"]::after {
content: " \f0da";
font-family: FontAwesome;
display: inline;
text-align: right;
padding-left: 5px;
}
/* level 1*/
#sidebar .list-group .collapse .list-group-item {
padding-left: 20px;
}
/* level 2*/
#sidebar .list-group .collapse > .collapse .list-group-item {
padding-left: 30px;
}
/* level 3*/
#sidebar .list-group .collapse > .collapse > .collapse .list-group-item {
padding-left: 40px;
}
#media (max-width:48em) {
/* overlay sub levels on small screens */
#sidebar .list-group .collapse.in, #sidebar .list-group .collapsing {
position: absolute;
z-index: 1;
width: 190px;
}
#sidebar .list-group > .list-group-item {
text-align: center;
padding: .75rem .5rem;
}
/* hide caret icons of top level when collapsed */
#sidebar .list-group > .list-group-item[aria-expanded="true"]::after,
#sidebar .list-group > .list-group-item[aria-expanded="false"]::after {
display:none;
}
}
/* change transition animation to width when entire sidebar is toggled */
#sidebar.collapse {
-webkit-transition-timing-function: ease;
-o-transition-timing-function: ease;
transition-timing-function: ease;
-webkit-transition-duration: .2s;
-o-transition-duration: .2s;
transition-duration: .2s;
}
#sidebar.collapsing {
opacity: 0.8;
width: 0;
-webkit-transition-timing-function: ease-in;
-o-transition-timing-function: ease-in;
transition-timing-function: ease-in;
-webkit-transition-property: width;
-o-transition-property: width;
transition-property: width;
}
main{
background-color:green;
}
</style>
<div class="container-fluid">
<div class="row">
<div class="col-md-3 col-1 pl-0 pr-0 collapse in" id="sidebar">
<div class="list-group panel">
<i class="fa fa-dashboard"></i> <span class="hidden-sm-down">Item 1</span>
<div class="collapse" id="menu1">
Subitem 1
<div class="collapse" id="menu1sub1">
Subitem 1 a
Subitem 2 b
Subitem 3 c
<div class="collapse" id="menu1sub1sub1">
Subitem 3 c.1
Subitem 3 c.2
</div>
Subitem 4 d
Subitem 5 e
<div class="collapse" id="menu1sub1sub2">
Subitem 5 e.1
Subitem 5 e.2
</div>
</div>
Subitem 2
Subitem 3
</div>
<i class="fa fa-film"></i> <span class="hidden-sm-down">Item 2</span>
<i class="fa fa-book"></i> <span class="hidden-sm-down">Item 3 </span>
<div class="collapse" id="menu3">
3.1
3.2
<div class="collapse" id="menu3sub2">
3.2 a
3.2 b
3.2 c
</div>
3.3
</div>
<i class="fa fa-heart"></i> <span class="hidden-sm-down">Item 4</span>
<i class="fa fa-list"></i> <span class="hidden-sm-down">Item 5</span>
<i class="fa fa-clock-o"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-th"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-gear"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-calendar"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-envelope"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-bar-chart-o"></i> <span class="hidden-sm-down">Link</span>
<i class="fa fa-star"></i> <span class="hidden-sm-down">Link</span>
</div>
</div>
<main class="col pl-2 pt-2">
<i class="fa fa-navicon fa-lg"></i>
<hr>
<div class="page-header">
<h1>Bootstrap 4 Sidebar Menu</h1>
</div>
<p class="lead">A responsive, multi-level vertical accordion.</p>
</main>
</div>
</div>
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