mediumDSA

What is binary search on the answer?

Q: What is binary search on the answer?

**Intuition.** Sometimes you binary-search a **value**, not an array index. It works whenever feasibility is **monotonic**: if some candidate answer works, every value past it also works (or every value before it). You search the answer range and use a cheap **feasibility check** at each midpoint to decide which half to keep. monotone feasibility → binary-search the threshold (Koko: speed 4) too slow (infeasible) <r

610 views

Understand the problem

Explain binary searching a value range.

binary-searchsearch-space

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Stuck? AI Nudge Available

Get a conceptual hint to guide your logic without spoiling the final implementation.

Study the solution

The solution is waiting

Give it an honest attempt first — then compare your thinking with the full walkthrough.

Read the code

Koko eating bananas

Run Playground

def min_eating_speed(piles, hours):
    def hours_needed(speed):
        return sum((p + speed - 1) // speed for p in piles)   # ceil division
    lo, hi = 1, max(piles)
    while lo < hi:
        mid = (lo + hi) // 2
        if hours_needed(mid) <= hours:
            hi = mid             # feasible — try slower
        else:
            lo = mid + 1         # too slow — speed up
    return lo


# --- demo ---
print(min_eating_speed([3, 6, 7, 11], 8))        # 4
print(min_eating_speed([30, 11, 23, 4, 20], 5))  # 30

Join the discussion

Discussion (0)

No responses yet. Be the first to share what you think.

How do you count unique paths in a grid?

How do you find the node where a linked list cycle begins?