         while i != 0 && j != 0 {
             if lengths[i &* columns &+ j] == lengths[(i &- 1) &* columns &+ j] {
                 i = i &- 1
-                indexOffset -= 1
                 index = self.index(self.startIndex, offsetBy: indexOffset)
             } else if lengths[i &* columns &+ j] == lengths[i &* columns &+ j &- 1] {
                 j = j &- 1

/**
An extension of `RangeReplaceableCollection`, which calculates the longest common subsequence between two collections.
*/
public extension RangeReplaceableCollection where Iterator.Element: Equatable {

    /**
    Returns the longest common subsequence between two collections.

    }
    
    /// Construct the `Diff` between two given collections.
    public init<C: Collection>(_ old: C, _ new: C) where C.Index == Index, C.Element: Equatable {
        self = old.diff(new)
    }
    
