I was asked the below question in my Google phone interview.

Problem: given a list of leaf nodes in a pyramid ，and a map which indicates what's the possible parent node given a left and right node. Return true if the one of leaf node could turn into the root node, Otherwise, return false.

'''

Example:

```
root
/ \
X X
```

/\ /

X X X

/ / /

A B C D

Map:

```
left: A | B | C | D
```

right ---------------------------------

A B | A or C | D | A

B D |B or C | A |

C B

D

'''

Note:1. If left child is B, right child is A, the parent node could be B or C

Refer: https://stackoverflow.com/questions/43432699/string-pyramid-transition-matrix