五种小div在大div中水平垂直居中方法

    *{
        padding: 0;
        margin: 0;
    }
        .parent_1{
            width: 200px;
            height: 200px;
            background: red;
            position: relative;
            margin-bottom: 10px;
        }
        .child_1{
            width: 100px;
            height: 100px;
            background: #000;
            position: absolute;
            left:0;
            right: 0;
            top: 0;
            bottom: 0;
            margin: auto;
        }
        .parent_2{
            width: 200px;
            height: 200px;
            background: red;
            display: table-cell;
            vertical-align: middle;
            text-align: center;
        }
        .child_2{
            width: 100px;
            height: 100px;
            background: #000;
            display: inline-block;
        }    
        .parent_3{
            width: 200px;
            height: 200px;
            background: red;
            display: flex;
            justify-content: center;
            align-items: center;
            margin-top: 10px;

        }
        .child_3{
            width: 100px;
            height: 100px;
            background: #000;
        }                                
        .parent_4{
            width: 200px;
            height: 200px;
            background: red;
            position: relative;
            margin-top: 10px;

        }
        .child_4{
            width: 100px;
            height: 100px;
            background: #000;
            position: absolute;
            left:50%;
            top:50%;
            margin-left:-50px;
            margin-top:-50px
        }
        .parent_5{
            width: 200px;
            height: 200px;
            background: red;
            margin-top: 10px;
            display: -webkit-box;
            -webkit-box-align: center;
            -webkit-box-pack: center;
        }
        .child_5{
            width: 100px;
            height: 100px;
            background: #000;
        }


<!--第一种方法 left bottom top right 0导致混乱后用margin:auto直接水平垂直居中-->
<div class="parent_1">
    <div class="child_1">                
    </div>
</div>
<!--第二种方法利用display:table-cell布局 display:inline-block布局-->

<div class="parent_2">
    <div class="child_2">                
    </div>
</div>
     <!--flex布局 justify-content:center align-items:center-->
        <div class="parent_3">
    <div class="child_3">                
    </div>
</div>
<!--第四种方法根据定位减去宽高-->
        <div class="parent_4">
    <div class="child_4">                
    </div>
</div>        
<!--弹性盒模型居中-->

 <div class="parent_5">
    <div class="child_5">                
    </div>
</div>