用第三种方案似乎也可以实现 而且简单

<style>

        #parent {

            display: table;

            width: 100%;

            table-layout: fixed;

        }

        #left,

        #center,

        #right {

            height: 300px;

        }

        #left {

            border: green solid 1px;

            color: green;

            width: 300px;

            display: table-cell;

        }

        #center {

            border: hotpink solid 1px;

            color: hotpink;

            display: table-cell;

        }

        #right {

            border: yellow solid 1px;

            color: yellow;

            width: 300px;

            display: table-cell;

        }

    </style>