There are other problems that allow for what is called a Polynomial-Time Approximation Scheme and the idea behind the polynomial-time approximation scheme is basically that if you put in more running time in to your algorithm, and that algorithm is called a polynomial-time approximation scheme, then you will get a better solution or a better guarantee for your solution, and depending on how good you want that guarantee to be, then again certain implications for the running time you have to put in. 