How hard is LeetCode 2936. Number of Equal Numbers Blocks?

LeetCode 2936. Number of Equal Numbers Blocks is rated Medium on LeetCode.

What is the time complexity of LeetCode 2936. Number of Equal Numbers Blocks?

The Python solution on this page runs in O(m \times \log n), where m is the number of different elements in the array num, and n is the length of the array num.

What is the space complexity of LeetCode 2936. Number of Equal Numbers Blocks?

The Python solution on this page uses O(1) auxiliary space.

What topics does LeetCode 2936. Number of Equal Numbers Blocks cover?

LeetCode 2936. Number of Equal Numbers Blocks is tagged Array, Binary Search and Interactive on LeetCode.

Is LeetCode 2936. Number of Equal Numbers Blocks a premium problem?

Yes. LeetCode 2936. Number of Equal Numbers Blocks is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.

Number of Equal Numbers Blocks — LeetCode 2936 Python Solution

MediumLeetCode PremiumArrayBinary SearchInteractive

Problem: #2936
Pattern: Monotonic Stack
Reading time: 3 min
Source: leetcode.com

The problem

You are given a 0-indexed array of integers, nums. The following property holds for nums: All occurrences of a value are adjacent.

Example

Input: nums = [3,3,3,3,3]
Output: 1
Explanation: There is only one block here which is the whole array (because all numbers are equal) and that is: [3,3,3,3,3]. So the answer would be 1.

Python solution

Python

# Definition for BigArray.
# class BigArray:
#     def at(self, index: long) -> int:
#         pass
#     def size(self) -> long:
#         pass
class Solution(object):
    def countBlocks(self, nums: Optional["BigArray"]) -> int:
        i, n = 0, nums.size()
        ans = 0
        while i < n:
            ans += 1
            x = nums.at(i)
            if i + 1 < n and nums.at(i + 1) != x:
                i += 1
            else:
                i += bisect_left(range(i, n), True, key=lambda j: nums.at(j) != x)
        return ans

Complexity

Measure	Complexity
Time	O(m \times \log n), where m is the number of different elements in the array num, and n is the length of the array num
Space	O(1) auxiliary

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 2936. Number of Equal Numbers Blocks is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The monotonic stack guide has the Python template for the pattern and the 225 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 2936. Number of Equal Numbers Blocks?: LeetCode 2936. Number of Equal Numbers Blocks is rated Medium on LeetCode.
What is the time complexity of LeetCode 2936. Number of Equal Numbers Blocks?: The Python solution on this page runs in O(m \times \log n), where m is the number of different elements in the array num, and n is the length of the array num.
What is the space complexity of LeetCode 2936. Number of Equal Numbers Blocks?: The Python solution on this page uses O(1) auxiliary space.
What topics does LeetCode 2936. Number of Equal Numbers Blocks cover?: LeetCode 2936. Number of Equal Numbers Blocks is tagged Array, Binary Search and Interactive on LeetCode.
Is LeetCode 2936. Number of Equal Numbers Blocks a premium problem?: Yes. LeetCode 2936. Number of Equal Numbers Blocks is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.