L16-MST

# Case 1 if a e t then the theorem is true already case

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Unformatted text preview: times: 3 Pick a cut (S, V S ) that respects A 4 Let e be min-weight edge over cut (S, V 5 A ⇥ A ⌅ {e} S) Prim’s algorithm General-MST-Strategy(G = (V, E )) 1 A⇥⇤ 2 repeat V 1 times: 3 Pick a cut (S, V S ) that respects A 4 Let e be min-weight edge over cut (S, V 5 A ⇥ A ⌅ {e} A is a subtree edge e is lightest edge that grows the subtree S) prim b 8 d g 7 10 a 8 3 c 5 e 9 12 2 9 11 3 1 i f 6 h prim b 8 d g 7 10 a 8 3 c 5 e 9 12 2 9 11 3 1 i f 6 h prim b 8 d g 7 10 a 8 3 c 5 e 9 12 2 9 11 3 1 i f 6 h prim b 8 d g 7 10 a 8 3 c 5 e 9 12 2 9 11 3 1 i f 6 h prim b 8 d g 7 10 a 8 3 c 5 e 9 12 2 9 11 3 1 i f 6 h implementation idea: implementation new data structure binary heap full tree, key value <= to key of children binary heap full tree, key value <= to key of children ! "# "" &! \$ "! '' % : binary heap full tree, key value <= to key of children ! "# \$ "" &! "! '' ( % : binary heap full tree, key value <= to key of children ! "# \$ "" &! ( '' "! % : binary heap full tree, key value <= to key of children how to extractmin? ! ( \$ "" &! "# '' "! % : binary heap full tree, key value <= to key of children how to extractmin? 24 ( \$ "" &! "# '' "! % : binary heap full tree, key value <= to key of children how to extractmin? \$ ( 24 "" &! "# '' "! % : binary heap full tree, key value <= to key of children how to extractmin? \$ how to decreasekey? ( % "" &! "# ) '' "! 24 : binary heap full tree, key value <= to key of children how to extractmin? \$ how to decreasekey? ) % "" &! "# ( '' "! 24 : implementation use a priority queue to keep track of light edges insert: makequeue: extractmin: decreasekey: algorithm implementation prim(G = (V, E )) 1Q ⇧ Q is a Priority Queue 2 Initialize each v ⇤ V with key kv ⇥, v nil 3 Pick a starting node r and set kr 0 4 Insert all nodes into Q with key kv . 5 while Q ⌅= ⇧ 6 do u extract-min(Q) 7 for each v ⇤ Adj (u) 8 do if v ⇤ Q and w(u, v ) < kv 9 then v u 10 decrease-key(Q, v, w(u, v )) Sets kv w(u, v ) prim b 8 d 0 g 7 10 a 8 3 c 5 e 9 12 2...
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