Comparing letters depends on the relative value of the letters. But for character sets like ascii you say that A > Z, a > z, and Z > a. I'll attach a little program that can compare strings and tell...

Lack of confidence in your algorithm is a serious flaw and you should make sure that it's correct. Do a quick test in your head with all permutations of three numbers.

{1,2,3}

s = 1
1 is not...

Probably because I don't know how to put it into perfect mathematical notation... Honestly, I have no idea what you're talking about.

I can remove the unused precision if it bothers you. ;)

x represents internal nodes, that's nodes with one or more children. y represents the rest of the nodes with no children, and they're called external nodes.

6
/ \
5 ...

To traverse a binary tree you have to touch every node in the tree once. From that you infer that the time complexity is O(n). You can take it further by postulating that because the recursive...

I don't think a program can do that except for the simplest and most obvious of bugs; the kind that compilers or semantic checkers already catch for you 100% of the time. Finding anything more...

For a queue just think of stuff where something goes in one end and out the other in order. For a stack just think of stuff where something goes in one end and out the same end in order.