@@ -96,3 +96,60 @@ public func part1() -> Int {
9696 search ( inputData ( ) , Set ( [ " AA " ] ) , 0 , " AA " , 29 , & result)
9797 return result
9898}
99+
100+ func paths( _ world: World , _ path: [ ( String , Int ) ] , _ cur: String , _ timeLeft: Int , _ result: inout [ [ ( String , Int ) ] ] ) {
101+ if timeLeft <= 0 {
102+ result. append ( path)
103+ return
104+ }
105+ if !path. contains ( where: { $0. 0 == cur } ) {
106+ paths ( world, path + [ ( cur, timeLeft) ] , cur, timeLeft - 1 , & result)
107+ } else {
108+ for n in world. costs [ cur] ! where !path. contains ( where: { $0. 0 == n. 0 } ) {
109+ paths ( world, path, n. 0 , timeLeft - n. 1 , & result)
110+ }
111+ }
112+ }
113+
114+ struct Path : Equatable {
115+ let path : [ String ]
116+ let points : Set < String >
117+ let flow : Int
118+
119+ init ( path: [ String ] , flow: Int ) {
120+ self . path = path
121+ self . flow = flow
122+ points = Set ( path)
123+ }
124+ }
125+
126+ public func part2( ) -> Int {
127+ let world = inputData ( )
128+ var allPaths = [ [ ( String, Int) ] ] ( )
129+ paths ( world, [ ( " AA " , 0 ) ] , " AA " , 25 , & allPaths)
130+ var computed : [ Path ] = allPaths. map { p in
131+ Path (
132+ path: p. reduce ( into: [ String] ( ) , { if " AA " != $1. 0 { $0. append ( $1. 0 ) } } ) ,
133+ flow: p. reduce ( 0 , { $0 + $1. 1 * ( world. flow [ $1. 0 ] ?? 0 ) } )
134+ )
135+ }
136+ var best = Dictionary < Set < String > , Path > ( )
137+ for p in computed {
138+ if let prev = best [ p. points] {
139+ if p. flow > prev. flow {
140+ best [ p. points] = p
141+ }
142+ } else {
143+ best [ p. points] = p
144+ }
145+ }
146+ computed = best. values. sorted ( by: { $0. flow < $1. flow } )
147+ var result = - 1
148+ for p in computed {
149+ for q in computed{
150+ guard p. points. intersection ( q. points) . isEmpty else { continue }
151+ result = max ( result, q. flow + p. flow)
152+ }
153+ }
154+ return result
155+ }
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