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2779. Number Of Adjacent Elements With The Same Color

Array

Problem - Number Of Adjacent Elements With The Same Color

Medium

You are given an integer n representing an array colors of length n where all elements are set to 0's meaning uncolored. You are also given a 2D integer array queries where queries[i] = [indexi, colori]. For the ith query:

  • Set colors[indexi] to colori.
  • Count the number of adjacent pairs in colors which have the same color (regardless of colori).

Return an array answer of the same length as queries where answer[i] is the answer to the ith query.

 

Example 1:

Input: n = 4, queries = [[0,2],[1,2],[3,1],[1,1],[2,1]]

Output: [0,1,1,0,2]

Explanation:

  • Initially array colors = [0,0,0,0], where 0 denotes uncolored elements of the array.
  • After the 1st query colors = [2,0,0,0]. The count of adjacent pairs with the same color is 0.
  • After the 2nd query colors = [2,2,0,0]. The count of adjacent pairs with the same color is 1.
  • After the 3rd query colors = [2,2,0,1]. The count of adjacent pairs with the same color is 1.
  • After the 4th query colors = [2,1,0,1]. The count of adjacent pairs with the same color is 0.
  • After the 5th query colors = [2,1,1,1]. The count of adjacent pairs with the same color is 2.

Example 2:

Input: n = 1, queries = [[0,100000]]

Output: [0]

Explanation:

After the 1st query colors = [100000]. The count of adjacent pairs with the same color is 0.

 

Constraints:

  • 1 <= n <= 105
  • 1 <= queries.length <= 105
  • queries[i].length == 2
  • 0 <= indexi <= n - 1
  • 1 <=  colori <= 105

Solutions

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class Solution:
    def colorTheArray(self, n: int, queries: List[List[int]]) -> List[int]:
        result = [0] * len(queries)
        nums = [0] * n
        val = 0
        for j, (i, colour) in enumerate(queries):
            if i > 0 and nums[i] and nums[i - 1] == nums[i]:
                val -= 1
            if i < n - 1 and nums[i] and nums[i + 1] == nums[i]:
                val -= 1
            if i > 0 and nums[i - 1] == colour:
                val += 1
            if i < n - 1 and nums[i + 1] == colour:
                val += 1
            result[j] = val
            nums[i] = colour
        return result

Submission Stats:

  • Runtime: 99 ms (54.56%)
  • Memory: 49.6 MB (94.47%)