Solved 9.1 find possible ways to jump up a flight of stairs if each time can hop 1, 2 or 3 steps. used DP
Solved 9.3 find the index i in a sorted array such that array[i] == i, used binary search ,
Solved 9.7 paint a graph, used the methods learned in CG class.   Stack adjacent runs to be painted, have an issue that some runs may be stacked twice, but not a big problem-- it would return quickly the second time trying to paint it.