title: Dijkstra's Algorithm Pseudocode Confusion
body: <p>I am trying to implement a version of Dijkstra's algorithm for the traveling salesman problem and I found this paper: <a href="https://www.researchgate.net/figure/Dijkstras-algorithm-for-many-targets-with-a-pruning-heuristic-An-upper-bound-B-for-d-v_fig2_257428759" rel="nofollow noreferrer">https://www.researchgate.net/figure/Dijkstras-algorithm-for-many-targets-with-a-pruning-heuristic-An-upper-bound-B-for-d-v_fig2_257428759</a></p>
  <p>I understand the algorithm but I am confused about what 'free' means in this pseudocode. Can anyone explain it to me?</p>
  <p>i.e. in the following lines:</p>
  <p>if u is free then STOP fl</p>
  <p>if v is free then B = min{c, b} fl</p>
  <p><a href="https://i.stack.imgur.com/NoB2f.png" rel="nofollow noreferrer">A Heuristic for Dijkstra's Algorithm with Many Targets (Pseudocode)</a></p>