2672. Number of Adjacent Elements With the Same Color | 1705

 1class Solution:
 2    def colorTheArray(self, n: int, queries: List[List[int]]) -> List[int]:
 3        # e.g. when changing index i to new:
 4        # check arr[i], store it old
 5        # check if arr[i-1] == old: pair -= 1
 6        # else  if arr[i-1] == new: pair += 1
 7        # check if arr[i+1] == old: pair -= 1
 8        # else  if arr[i+1] == new: pair += 1
 9        # also we don't care about uncolored.
10        # also if old == new we just do nothing
11
12        arr = [0] * n
13        result = [0]
14
15        for i, new_v in queries:
16            pair_delta = 0
17            old_v = arr[i]
18
19            if old_v != new_v:
20                if i - 1 > -1 and arr[i - 1] != 0:
21                    if arr[i - 1] == old_v:
22                        pair_delta -= 1
23                    elif arr[i - 1] == new_v:
24                        pair_delta += 1
25                if i + 1 < n and arr[i + 1] != 0:
26                    if arr[i + 1] == old_v:
27                        pair_delta -= 1
28                    elif arr[i + 1] == new_v:
29                        pair_delta += 1
30                arr[i] = new_v
31
32            result.append(result[-1] + pair_delta)
33
34        return result[1:]