title: Is it necessary for NP problems to be decision problems ?
body: <p>Professor Tim Roughgarden from Stanford University while teaching a <a href="https://class.coursera.org/algo2-2012-001/class/index" rel="nofollow">MOOC</a> said that solutions to problems in the class NP must be polynomial in length. But the <a href="https://en.wikipedia.org/wiki/NP_%28complexity%29" rel="nofollow">wikipedia article</a> says that NP problems are decision problems. So what type of problems are basically in the class NP ? And is it unnecessary to say that solutions to such problems have a polynomial length output(as decision problems necessarily output either 0 or 1) ? </p>