A* Search Algorithm

Question

I would like to have something clarified with regards to the following A* Search example:

Answer 1

This is taking the current best item, removing it, and replacing it with the expansion (inserting the new items into appropriate positions in the list). Think of it like this:

Expand S:

• {S,A} f = 1+5 = 6
• {S,B} f = 2+6 = 8

Expand A:

• {S,A} f = 1+5 = 6
• {S,B} f = 2+6 = 8
• {S,A,X} f = (1+4)+5 = 10
• {S,A,Y} f = (1+7)+8 = 16

Expand B:

• {S,B} f = 2+6 = 8
• {S,A,X} f = (1+4)+5 = 10
• {S,B,C} f = (2+7)+4 = 13
• {S,A,Y} f = (1+7)+8 = 16
• {S,B,D} f = (2+1)+15 = 18