1. DFS
import Data.Ix
import Graph
import Stack
depthFirstSearch :: Ix a => a -> Graph a a -> [a]
depthFirstSearch start g = dfs [start] []
where
dfs [] vis = vis
dfs (c:cs) vis | elem c vis = dfs cs vis
| otherwise = dfs ((adjacent g c) ++ cs) (vis ++ [c])
depthFirstSearch' :: Ix a => a -> Graph a a -> [a]
depthFirstSearch' start g = reverse $ dfs [start] []
where
dfs [] vis = vis
dfs (c:cs) vis | elem c vis = dfs cs vis
| otherwise = dfs ((adjacent g c) ++ cs) (c:vis)
depthFirstSearch'' :: Ix a => a -> Graph a a -> [a]
depthFirstSearch'' start g = reverse $ dfs (push start emptyStack) []
where
dfs s vis | (stackEmpty s) = vis
| elem (top s) vis = dfs (pop s) vis
| otherwise = let c = top s
in
dfs (foldr push (pop s) (adjacent g c))
(c:vis)
2. BFS
import Data.Ix
import Graph
import Queue
breadFirstSearch :: Ix a => a -> Graph a a -> [a]
breadFirstSearch start g = reverse (bfs (enqueue start emptyQueue) [])
where
bfs q vis | (queueEmpty q) = vis
| elem (front q) vis = bfs (dequeue q) vis
| otherwise = let c = front q
in
bfs (foldr enqueue
(dequeue q)
(adjacent g c))
(c:vis)
參考
Algorithms: A Functional Programming Approach
Stack
Queue
Graph - 鄰接表
Graph - 鄰接矩陣
