algorithm - Function of this graph pseudocode - 


procedure explore(g; v) input: g = (v;e) graph; v 2 v output: visited(u) set true nodes u reachable v   visited(v) = true previsit(v) each edge (v; u) 2 e: if not visited(u): explore(u) postvisit(v)

all pseudocode find 1 path right? nothing while backtracking if i'm not wrong?

it explores graph (it doesn't return path) - that's reachable starting vertex explored , have corresponding value in visited set (not vertices corresponding 1 of paths).

it moves on next edge while backtracking ... , postvisit.

so if we're @ a, has edges b, c , d, we'll start going b, then, when return a, we'll go c (if hasn't been visited already), , go d after return a 2nd time.

it's called depth-first search, in case wondering. wikipedia gives example of order in vertices explored in tree: (the numbers correspond visit order, start @ 1)

in above, you're not exploring vertices going down left (1-4), after 4 go 3 visit 5, 2 visit 6, , on, until 12 visited.

with regard previsit , postvisit - previsit happen when first vertex, postvisit happen after we've explored of it's children (and descendants in corresponding dfs tree). so, in above example, 1, previsit happen right @ start, post-visit happen @ end, because vertices children of 1 or descendants of children. order go like:

pre 1, pre 2, pre 3, pre 4, post 4, pre 5, post 5, post 3, pre 6, post 6, post 2, ...


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