The Ordered Search Algorithm

  1. Put the start node s on open; compute f( s).

  2. While open is non-empty,
    1. Remove the lowest-cost node n from open; put n on closed. If n is a goal, terminate with success. The solution path is given by the pointers from n back to the start node.

    2. Expand node n (generate its successors). For each successor node m,
      1. Compute f( m).

      2. If m is neither on open nor on closed, place m on open so that open remains ordered. Put a pointer from m back to n and record the operator used.

      3. If m is already on open or closed, and the path to m just found is better than the one previously found, change the cost value and pointer of node m to the new values and put m on open.

  3. open is empty; terminate with failure.

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