# Errata, Lecture Videos

Course Introduction (3:28)

 Displayed: A video compression artifact has removed the path between the two nodes. Fixed: Eliminate video artifict.
Reported by Kevin Wayne, 01-Jan-14.

Course Introduction (7:30)

 Displayed: http://www.algs4.princeton.edu. Fixed: http://algs4.cs.princeton.edu.
Reported by Wei En, 30-Jan-14.

Quick-Union Improvements

 Spoken: Ackermann function Fixed: Inverse Ackermann function
Reported by Kevin Wayne, 01-Jan-14.

Sorting Introduction (1:00)

 Spoken: Data is read from standard input Fixed: Data is read from StdRandom.uniform()
Reported by Kevin Wayne, 01-Jan-14.

Shellsort (3:02)

 Spoken: Use Shellsort to sort subsequences Fixed: Use selection sort to sort subsequences
Reported by Kevin Wayne, 01-Jan-14.

Duplicate Keys

 Displayed: Dijkstra 3-way partitioning demo stops when i == gt. Fixed: Dijkstra 3-way partitioning demo should go one extra step so that i > gt.
Reported by Kevin Wayne, 01-Jan-14.

Deletion in BSTs (8:20)

 Spoken: If you randomly choose between predecessor and successor in Hibbard deletion, then the height of the resulting tree is sqrt(N). Fixed: The conjecture is that the height of the resulting tree is log(N).
Reported by Kevin Wayne, 01-Jan-14.

K-d Trees (8:30 to 9:10)

 Spoken: Above/upper Fixed: Below/lower
Reported by Kevin Wayne, 01-Jan-14.

K-d Trees (19:19)

 Displayed: The left subtree (below the splitting line) of 5 should be explored before the right subtree (above the splitting line) Fixed: The right subtree should be explored before the left subtree
Reported by Kevin Wayne, 01-Jan-14.

Prim's Algorithm (21:55)

 Displayed: The edge 4-7 (0.37) does not replace the edge 0-4 (0.38) on the priority queue. Fixed: The edge 4-7 (0.37) should replace the edge 0-4 (0.38) on the priority queue. Edge 4-7 should remain on the priority queue until edge 4-5 (0.35) replaces it.
Reported by Kevin Wayne, 01-Jan-14.

Classifying Problems (6:26)

 Displayed: The reduction is unnecessarily complicated. Fixed: Simplify it.
Reported by Kevin Wayne, 01-Jan-14.