Interviews looming. You’re sweating over LeetCode 875, Koko Eating Bananas. Real devs — not theorists — know this one’s a trap for the lazy.
Piles of bananas. Koko chomps one pile per hour, at some speed k bananas/hour. Finish all in h hours? Find the smallest k. Guards eat the rest if late. Brutish story. Classic optimization.
Find the minimum eating speed (bananas per hour) such that Koko can eat all banana piles within h hours, where she can only eat from one pile per hour.
That’s the hook. Straight from the problem. No fluff.
Why Does LeetCode 875 Trip Up Job Hunters?
Look. Most smash it with loops. Try k=1, k=2, up to max pile. Hours exceed h? Bump k. Works for toys. Crumbles on real inputs — n=10^4 piles, max pile 10^9. Timeouts galore. Interviewers smirk.
Binary search flips it. Search space: 1 to max(piles). Midpoint guess. Calc hours with ceiling div: (pile + mid -1 ) // mid per pile, sum ‘em. Too slow? Hunt higher. Fine? Hunt lower. Log time. Boom.
Here’s the code — lean, mean.
class Solution: def minEatingSpeed(self, piles: List[int], h: int) -> int: left, right = 1, max(piles) while left < right: mid = left + (right - left) // 2 hours = sum((pile + mid - 1) // mid for pile in piles) if hours > h: left = mid + 1 else: right = mid return left
Punchy. O(n log m). Space O(1). No allocations bloating your stack.
But wait — why ceiling? (pile // mid) floors wrong. Leftover bananas? She finishes next hour. So +mid-1 tricks integer div. Sneaky. Smart.
Is Binary Search Overkill for Bananas?
Nah. Monotonic magic: higher k always <= hours. Perfect for bin search. Brute force? O(max_pile * n). Disastrous.
Trace it. Say piles = [3,6,7,11], h=8. Max=11. left=1, right=11.
Mid=6. Hours: ceil(3/6)=1, 6/6=1, 7/6=2, 11/6=2. Total 6 <=8. right=6.
Mid=3 (1+ (6-1)//2? Wait, 1+2=3). Hours:1,2,3,4=10>8. left=4.
Mid=4 (4+(6-4)//2=5? Recalc. left=4,right=6, mid=5. Hours:1,2,2,3=8<=8. right=5.
left=4,right=5. mid=4. Hours:1,2,2,3=8<=8. right=4.
left==right=4. Done. She eats at 4/hour.
Visuals help. TraceLit steps every line — piles glow, mids shift, hours tally. No mental gymnastics.
Critics whine: LeetCode’s monkey tales infantilize algos. Fair. But ignore story — grok the math. Binary search isn’t new. Knuth codified it ‘68, TAOCP Vol 3. Your interviewer? Probably read it. You? Better pretend.
Unique twist: This mirrors real ops research — factory throughput, truck loading. Minimize speed (cost) for deadline. Google it post-interview. Sounds smart.
Corporate spin? LeetCode hypes weekly contests. Cute. But 875’s evergreen. Taught me ceilings early — saved ass in prod code.
Dry humor: Koko’s no glutton. Optimal eater. Unlike that dev looping to infinity.
Deeper. What if h < piles.length? Impossible, k huge. Edge: h=1, one pile — k=pile. Guard starves.
Test cases. [30,11,23,4,20], h=5. Ans=30? Nah, calc: try 23? Hours high. 30 works? Wait, bin search finds 30? No, lower. Actually 23? Trace it yourself.
Point: Don’t eyeball. Code it. LeetCode’s validator bites.
Can You Skip LeetCode 875 Entirely?
Dream on. Medium binary search tag. 50% acceptance? Half fail. FAANG filters it.
Prediction: With AI coders rising, humans win on traces — explain why left=mid+1, not mid. Robots regurgitate. You? “Monotonic, halves search space.”
TraceLit? Gimmick? Nah — watches variables mutate. Like gdb, but kindergarten colors. Open it. Step through. Patterns stick.
Wander a bit: Ever ceiling-div wrong? Burned me once — scheduler overshot slots. Lesson: Math first, code second.
Humor: Koko unionizes? Demands fair piles. Bin search union-busts.
Stretch it. Scale: n=10^5? Sum’s bottleneck. Prefix sums? Overkill — log(10^9)=30 passes, 30*n=3e6 fine.
History nod: D&C divide et impera, Romans knew. Bin search? Sorted lists eternal.
Skepticism: LeetCode premiums? Paywall traces? TraceLit free alt? Check.
Real talk — grind 875, own it. Interviewer nods. Job closer.
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Frequently Asked Questions
What is the solution to LeetCode 875 Koko Eating Bananas?
Binary search on speed 1 to max(piles). Ceiling div hours per pile, sum. Adjust bounds.
Why use binary search in Koko Eating Bananas?
Monotonic: higher speed <= hours. Log time beats linear scan on huge max.
How to calculate hours needed for speed k?
Sum over piles: (pile + k - 1) // k. Ceiling without floats.
