Q1:
Is possible. Give 2 nodes (a,b), (c,d). Judge whether it's possible to reach(c,d) from (a,b).
There are only 4 ways to move(a,b)->(a+b,b), (a+a,b),(a,b+a),(a,b+b)
Q2:
K smallest substring
Q3:
Tiling with Dominoes
Q4：
Preprocess Date
Q5:
Shared Interest