3160. Find the Number of Distinct Colors Among the Balls

Problem Link

Description

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You are given an integer limit and a 2D array queries of size n x 2.

There are limit + 1 balls with distinct labels in the range [0, limit]. Initially, all balls are uncolored. For every query in queries that is of the form [x, y], you mark ball x with the color y. After each query, you need to find the number of distinct colors among the balls.

Return an array result of length n, where result[i] denotes the number of distinct colors after ith query.

Note that when answering a query, lack of a color will not be considered as a color.

 

Example 1:

Input: limit = 4, queries = [[1,4],[2,5],[1,3],[3,4]]

Output: [1,2,2,3]

Explanation:

• After query 0, ball 1 has color 4.
• After query 1, ball 1 has color 4, and ball 2 has color 5.
• After query 2, ball 1 has color 3, and ball 2 has color 5.
• After query 3, ball 1 has color 3, ball 2 has color 5, and ball 3 has color 4.

Example 2:

Input: limit = 4, queries = [[0,1],[1,2],[2,2],[3,4],[4,5]]

Output: [1,2,2,3,4]

Explanation:

• After query 0, ball 0 has color 1.
• After query 1, ball 0 has color 1, and ball 1 has color 2.
• After query 2, ball 0 has color 1, and balls 1 and 2 have color 2.
• After query 3, ball 0 has color 1, balls 1 and 2 have color 2, and ball 3 has color 4.
• After query 4, ball 0 has color 1, balls 1 and 2 have color 2, ball 3 has color 4, and ball 4 has color 5.

 

Constraints:

• 1 <= limit <= 109
• 1 <= n == queries.length <= 105
• queries[i].length == 2
• 0 <= queries[i][0] <= limit
• 1 <= queries[i][1] <= 109

Solution

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Python3

class Solution:
    def queryResults(self, limit: int, queries: List[List[int]]) -> List[int]:
        count = Counter()
        unique = 0
        prev = {}
        res = []
 
        for ball, color in queries:
            if ball in prev:
                count[prev[ball]] -= 1
                if count[prev[ball]] == 0:
                    unique -= 1
            
            count[color] += 1
            prev[ball] = color
            
            if count[color] == 1:
                unique += 1
            
            res.append(unique)
 
        return res