Amazon Software Engineer interview questions

Find vertical sums of given binary tree.

Let's say there is a river that is n meters wide. At every meter from the starting shore, there may or may not be a stone enough for frog to sit. Now a frog needs to cross the river. However the frog has the limitation that if it has just jumped x meters, then it can take next jump only of size (x - 1), x or (x + 1) meters. First jump can be of only 1 meter when starting from shore. Assume frog can see all stone from this shore to opposite shore. Can frog determine whether it can make it to the other end or not.

Given a number tell its nearest bigger permutation.