How are polymers classified on the basis of structure?

Polymers are classified on the basis of structure into the following three types:
$1.$ Linear polymers:
These polymers consist of long and straight chains. They are well-packed and have high densities,tensile strength,and melting points. Examples include high-density polythene $(HDP)$,polyvinyl chloride $(PVC)$,etc.
$2.$ Branched chain polymers:
These polymers consist of linear chains having some branches of different lengths. Due to branching,they do not pack well and thus have lower densities and melting points. Examples include low-density polythene $(LDP)$,amylopectin,etc.
$3.$ Cross-linked or Network polymers:
These polymers are formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains. This results in a three-dimensional network structure. These are hard,rigid,and brittle. Examples include bakelite,melamine-formaldehyde resin,etc.