Medium
Binary Search
Koko Eating Bananas
Binary search the answer: eating speed is monotonic in whether she finishes in time.
Approach
The feasible speeds form a monotonic predicate — any speed fast enough works, slower ones don't. Binary search speeds between 1 and max(pile); for each candidate, sum the hours needed and check against h. Return the smallest feasible speed.
Time complexity
O(n log max)
Space complexity
O(1)
Common mistake
Searching values in the array instead of the answer space [1, max pile] — this is 'binary search on the answer'.
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