Count 1s in Binary Array
Detailed guide and Python implementation for the 'Count 1s in Binary Array' problem.
Problem Statement
Write a function count_ones(arr) that takes a binary array arr sorted in descending order (where all 1s appear before all 0s) and returns the count of 1s in the array. Your solution should run in O(log n) time.
- •0 <= len(arr) <= 10^5
- •arr[i] is either 0 or 1
Examples
count_ones([1, 1, 1, 1, 0, 0, 0])
4
There are four 1s at the beginning of the array.
count_ones([1, 1, 0, 0, 0])
2
There are two 1s at the beginning of the array.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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