go-median-two-sorted-logmin

2 answer(s)gogo1.26gogo1.26

📦 Source in repository (JSON)

Answer 1

Solved and verified. Files in ~:

median.go — the medianOfTwoSortedArrays implementation (O(log(min(n,m))), O(1) space)
median_test.go — targeted edge cases + 5,050 randomized brute-force cross-checks
SOLUTION.md — self-contained writeup: root-cause analysis, the exact fix, and verification
go.mod — module median, go 1.26

Key design points that address the stated failure modes:

Partition invariant — binary search over i ∈ [0, n] (count of nums1 elements in the left half) with j = (n+m+1)/2 - i, stopping when nums2[j-1] <= nums1[i] and nums1[i-1] <= nums2[j] hold exactly as specified.
Empty-array safety — boundary guards i < n && j > 0 / i > 0 && j < m act as ±inf sentinels and prevent out-of-range indexing; n == 0 executes the loop exactly once; a total == 0 early return prevents nums2[-1] panics.
Overflow avoidance — low + (high-low)/2 for the midpoint and (float64(leftMax) + float64(rightMin)) / 2.0 for the even case so leftMax+rightMin never wraps in int.
Odd/even correctness — odd total returns leftMax; even total averages leftMax and rightMin (verified [1,2]+[3,4] → 2.5).

Verification (all green): gofmt, go vet, go test, and go test -race — including math.MaxInt/MinInt overflow cases, duplicates, negatives, single elements, both-empty, and randomized cross-checks against a brute-force sorted-median reference (zero mismatches).

Evidence & signatures

# Evidence
- Problem class: go-median-two-sorted-logmin
- Model: openrouter/deepseek/deepseek-v4-flash-0731
- Solved: 2026-08-19T22:10:55.446Z
- Verification: solution produced by pi in sandbox; see signatures.json

{"description": "Implement medianOfTwoSortedArrays(nums1, nums2 []int) float64 that returns the median of two sorted arrays in O(log(min(n,m))) time via binary search on the smaller array, handling empty arrays, duplicates, and odd/even total lengths. The partition-based solution must keep the left halves of both arrays as the largest valid split with nums1[i-1] <= nums2[j] and nums2[j-1] <= nums1[i]; classic failure modes are off-by-one partition indices, infinite loops when the smaller array is empty, and overflow in the midpoint calculation. Return exact float64 values, e.g. [1,2] and [3,4] must yield 2.5, and single-element arrays must not panic on out-of-range indexing.", "environment": "go1.26", "language": "go", "model": "openrouter/deepseek/deepseek-v4-flash-0731", "problem_class": "go-median-two-sorted-logmin", "provider": "openrouter", "solved_at": "2026-08-19T22:10:55.447Z", "version": "1.26"}

Answer 2

Solved and verified. Files in ~:

median.go — the medianOfTwoSortedArrays implementation (O(log(min(n,m))), O(1) space)
median_test.go — targeted edge cases + 5,050 randomized brute-force cross-checks
SOLUTION.md — self-contained writeup: root-cause analysis, the exact fix, and verification
go.mod — module median, go 1.26

Key design points that address the stated failure modes:

Partition invariant — binary search over i ∈ [0, n] (count of nums1 elements in the left half) with j = (n+m+1)/2 - i, stopping when nums2[j-1] <= nums1[i] and nums1[i-1] <= nums2[j] hold exactly as specified.
Empty-array safety — boundary guards i < n && j > 0 / i > 0 && j < m act as ±inf sentinels and prevent out-of-range indexing; n == 0 executes the loop exactly once; a total == 0 early return prevents nums2[-1] panics.
Overflow avoidance — low + (high-low)/2 for the midpoint and (float64(leftMax) + float64(rightMin)) / 2.0 for the even case so leftMax+rightMin never wraps in int.
Odd/even correctness — odd total returns leftMax; even total averages leftMax and rightMin (verified [1,2]+[3,4] → 2.5).

Evidence & signatures

# Evidence
- Problem class: go-median-two-sorted-logmin
- Model: openrouter/deepseek/deepseek-v4-flash-0731
- Solved: 2026-08-19T22:10:55.446Z
- Verification: solution produced by pi in sandbox; see signatures.json

{"description": "Implement medianOfTwoSortedArrays(nums1, nums2 []int) float64 that returns the median of two sorted arrays in O(log(min(n,m))) time via binary search on the smaller array, handling empty arrays, duplicates, and odd/even total lengths. The partition-based solution must keep the left halves of both arrays as the largest valid split with nums1[i-1] <= nums2[j] and nums2[j-1] <= nums1[i]; classic failure modes are off-by-one partition indices, infinite loops when the smaller array is empty, and overflow in the midpoint calculation. Return exact float64 values, e.g. [1,2] and [3,4] must yield 2.5, and single-element arrays must not panic on out-of-range indexing.", "environment": "go1.26", "language": "go", "model": "openrouter/deepseek/deepseek-v4-flash-0731", "problem_class": "go-median-two-sorted-logmin", "provider": "openrouter", "solved_at": "2026-08-19T22:10:55.447Z", "version": "1.26"}

Generated from the verified corpus · MIT licensedBack to the catalog