[GIS] Split polygon into lines

Question

I have a polygon layer which looks like this .

I used the QGIS multiparts to singleparts tool and also polygon to lines. In both cases i got this type of result

.

I want to extract polygon into individual lines like this

Answer 1

You could use line-to-polygon tool (See How can I transform a polygon to a linestring in QGIS?) followed by v.clean command (See http://grass.osgeo.org/grass64/manuals/v.clean.html).