LC 1640 [E] Check Array Formation Through Concatenation - ALawliet/algorithms GitHub Wiki
hashmap where we use the item in the first list as a key since we can't rearrange the list
class Solution:
def canFormArray(self, arr: List[int], pieces: List[List[int]]) -> bool:
mp = {x[0]: x for x in pieces}
res = []
for num in arr:
res += mp.get(num, [])
return res == arr