title: Calculating complexity of recurrence
body: <p>I am having trouble understanding the concept of recurrences. Given you have <code>T(n) = 2T(n/2) +1</code> how do you calculate the complexity of this relationship? I know in mergesort, the relationship is <code>T(n) = 2T(n/2) + cn</code> and you can see that you have a tree with depth log2^n and cn work at each level. But I am unsure how to proceed given a generic function. Any tutorials available that can clearly explain this?</p>