css画三角形，对角 √ 勾形

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.selected{

        border-color: #5FB878;

    }

 

    .selected:after {

        content: "";

        position: absolute;

        top: 0;

        right: 0;

        border-top: 30px solid #5FB878;

        border-left: 30px solid transparent;

    }

 

    .selected:before {

        content: '';

        position: absolute;

        width: 14px;

        height: 8px;

        background: transparent;

        top: 4px;

        right: 1px;

        border: 2px solid white;

        border-top: none;

        border-right: none;

        -webkit-transform: rotate(-55deg);

        -ms-transform: rotate(-55deg);

        transform: rotate(-55deg);

        z-index: 9;

    }

　　最终效果