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fix(diff): correct overlap detection and bounds in linear space Myers #46

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Merged
KimNorgaard merged 2 commits into from
Mar 18, 2026
Merged

fix(diff): correct overlap detection and bounds in linear space Myers #46

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fix(diff): correct overlap detection and bounds in linear space Myers
KimNorgaard Mar 18, 2026
c5b4151
chore: add comments
KimNorgaard Mar 18, 2026
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8 changes: 5 additions & 3 deletions diff/myers/myers.go
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Original file line number Diff line number Diff line change
Expand Up @@ -339,11 +339,13 @@ func findMiddleSnake(a, b []string, aStart, aEnd, bStart, bEnd int) snake { //re
// vr: Reverse search (from bottom-right)
// Size needs to accommodate k ranging from -maxDiff to +maxDiff.
vectorSize := 2*maxDiff + 1
offset := maxDiff
if delta > 0 {
vectorSize += delta // Ensure space for reverse search diagonals
} else if delta < 0 {
vectorSize -= delta // delta is negative, so this increases the size
offset -= delta // delta is negative, so this increases the offset
}
// offset: Used to map diagonal k (which can be negative) to non-negative array indices.
offset := maxDiff

vf := make([]int, vectorSize)
vr := make([]int, vectorSize) // Stores relative x-coordinates within the n x m grid
Expand Down Expand Up @@ -448,7 +450,7 @@ func findMiddleSnake(a, b []string, aStart, aEnd, bStart, bEnd int) snake { //re
// Overlap Check
// Overlap check
if delta%2 != 0 && k >= delta-(d-1) && k <= delta+(d-1) {
reverseIdx := offset + (delta - k)
reverseIdx := offset + k
if reverseIdx >= 0 && reverseIdx < vectorSize {
reverseX := vr[reverseIdx]
if reverseX >= 0 && x >= reverseX {
Expand Down