Why A full-wave rectifier uses both halves of the input waveform: the positive half passes through directly, and the negative half is inverted and delivered to the load as well. Since every part of the input cycle contributes output current, all 360 degrees of the AC cycle is converted. That is why a full-wave supply has twice the ripple frequency (120 Hz from 60 Hz mains) and is easier to filter than a half-wave supply.
Watch out The 180 degree answer describes a half-wave rectifier, which passes only one polarity and leaves the other half of the cycle blocked.
Half-wave = half a cycle = 180 degrees; full-wave = full cycle = 360 degrees.