o 3ήc*2@sjdZddlmZddlZgdZdddZdddZdd d Zdd d Z dd dZ dddZ dddZ dS)z@Basic algorithms for depth-first searching the nodes of a graph.) defaultdictN) dfs_edgesdfs_treedfs_predecessorsdfs_successorsdfs_preorder_nodesdfs_postorder_nodesdfs_labeled_edgesc cs|dur|}n|g}t}|durt|}|D]U}||vrq||||t||fg}|rm|d\}}} z&t| } | |vr\|| fV|| |dkr\|| |dt|| fWn tyj|Ynw|s0qdS)aIIterate over edges in a depth-first-search (DFS). Perform a depth-first-search over the nodes of `G` and yield the edges in order. This may not generate all edges in `G` (see `~networkx.algorithms.traversal.edgedfs.edge_dfs`). Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search and yield edges in the component reachable from source. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Yields ------ edge: 2-tuple of nodes Yields edges resulting from the depth-first-search. Examples -------- >>> G = nx.path_graph(5) >>> list(nx.dfs_edges(G, source=0)) [(0, 1), (1, 2), (2, 3), (3, 4)] >>> list(nx.dfs_edges(G, source=0, depth_limit=2)) [(0, 1), (1, 2)] Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in PADS [1]_, with modifications to allow depth limits based on the Wikipedia article "Depth-limited search" [2]_. See Also -------- dfs_preorder_nodes dfs_postorder_nodes dfs_labeled_edges :func:`~networkx.algorithms.traversal.edgedfs.edge_dfs` :func:`~networkx.algorithms.traversal.breadth_first_search.bfs_edges` References ---------- .. [1] http://www.ics.uci.edu/~eppstein/PADS .. [2] https://en.wikipedia.org/wiki/Depth-limited_search Nsetlenadditernextappend StopIterationpop Gsource depth_limitnodesvisitedstartstackparent depth_nowchildrenchildr!W/tmp/pip-target-vg8gfxp4/lib/python/networkx/algorithms/traversal/depth_first_search.pyrs86     rcCs<t}|dur||n|||t||||S)aReturns oriented tree constructed from a depth-first-search from source. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- T : NetworkX DiGraph An oriented tree Examples -------- >>> G = nx.path_graph(5) >>> T = nx.dfs_tree(G, source=0, depth_limit=2) >>> list(T.edges()) [(0, 1), (1, 2)] >>> T = nx.dfs_tree(G, source=0) >>> list(T.edges()) [(0, 1), (1, 2), (2, 3), (3, 4)] See Also -------- dfs_preorder_nodes dfs_postorder_nodes dfs_labeled_edges edge_dfs bfs_tree N)nxDiGraphadd_nodes_fromadd_nodeadd_edges_fromr)rrrTr!r!r"rbs $  rcCsddt|||DS)aReturns dictionary of predecessors in depth-first-search from source. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- pred: dict A dictionary with nodes as keys and predecessor nodes as values. Examples -------- >>> G = nx.path_graph(4) >>> nx.dfs_predecessors(G, source=0) {1: 0, 2: 1, 3: 2} >>> nx.dfs_predecessors(G, source=0, depth_limit=2) {1: 0, 2: 1} Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in `PADS`_, with modifications to allow depth limits based on the Wikipedia article "`Depth-limited search`_". .. _PADS: http://www.ics.uci.edu/~eppstein/PADS .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search See Also -------- dfs_preorder_nodes dfs_postorder_nodes dfs_labeled_edges edge_dfs bfs_tree cSsi|]\}}||qSr!r!).0str!r!r" sz$dfs_predecessors..)r)rrrr!r!r"rs/rcCs6tt}t|||dD] \}}|||q t|S)aReturns dictionary of successors in depth-first-search from source. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- succ: dict A dictionary with nodes as keys and list of successor nodes as values. Examples -------- >>> G = nx.path_graph(5) >>> nx.dfs_successors(G, source=0) {0: [1], 1: [2], 2: [3], 3: [4]} >>> nx.dfs_successors(G, source=0, depth_limit=2) {0: [1], 1: [2]} Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in `PADS`_, with modifications to allow depth limits based on the Wikipedia article "`Depth-limited search`_". .. _PADS: http://www.ics.uci.edu/~eppstein/PADS .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search See Also -------- dfs_preorder_nodes dfs_postorder_nodes dfs_labeled_edges edge_dfs bfs_tree rr)rlistrrdict)rrrdr*r+r!r!r"rs/rcCtj|||d}dd|DS)aGenerate nodes in a depth-first-search post-ordering starting at source. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- nodes: generator A generator of nodes in a depth-first-search post-ordering. Examples -------- >>> G = nx.path_graph(5) >>> list(nx.dfs_postorder_nodes(G, source=0)) [4, 3, 2, 1, 0] >>> list(nx.dfs_postorder_nodes(G, source=0, depth_limit=2)) [1, 0] Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in `PADS`_, with modifications to allow depth limits based on the Wikipedia article "`Depth-limited search`_". .. _PADS: http://www.ics.uci.edu/~eppstein/PADS .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search See Also -------- dfs_edges dfs_preorder_nodes dfs_labeled_edges edge_dfs bfs_tree r-cs"|] \}}}|dkr|VqdS)reverseNr!r)uvr0r!r!r" & z&dfs_postorder_nodes..r#r rrredgesr!r!r"r/rcCr1)aGenerate nodes in a depth-first-search pre-ordering starting at source. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search and return nodes in the component reachable from source. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- nodes: generator A generator of nodes in a depth-first-search pre-ordering. Examples -------- >>> G = nx.path_graph(5) >>> list(nx.dfs_preorder_nodes(G, source=0)) [0, 1, 2, 3, 4] >>> list(nx.dfs_preorder_nodes(G, source=0, depth_limit=2)) [0, 1, 2] Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in `PADS`_, with modifications to allow depth limits based on the Wikipedia article "`Depth-limited search`_". .. _PADS: http://www.ics.uci.edu/~eppstein/PADS .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search See Also -------- dfs_edges dfs_postorder_nodes dfs_labeled_edges bfs_edges r-csr2)forwardNr!r4r!r!r"r7Yr8z%dfs_preorder_nodes..r9r:r!r!r"r)r<rc cs |dur|}n|g}t}|durt|}|D]u}||vrq||dfV||||t||fg}|r|d\}}} z.t| } | |vrM|| dfVn|| dfV|| |dkrj|| |dt|| fWnty||r|dd|dfVYnw|s6||dfVqdS)a Iterate over edges in a depth-first-search (DFS) labeled by type. Parameters ---------- G : NetworkX graph source : node, optional Specify starting node for depth-first search and return edges in the component reachable from source. depth_limit : int, optional (default=len(G)) Specify the maximum search depth. Returns ------- edges: generator A generator of triples of the form (*u*, *v*, *d*), where (*u*, *v*) is the edge being explored in the depth-first search and *d* is one of the strings 'forward', 'nontree', or 'reverse'. A 'forward' edge is one in which *u* has been visited but *v* has not. A 'nontree' edge is one in which both *u* and *v* have been visited but the edge is not in the DFS tree. A 'reverse' edge is on in which both *u* and *v* have been visited and the edge is in the DFS tree. Examples -------- The labels reveal the complete transcript of the depth-first search algorithm in more detail than, for example, :func:`dfs_edges`:: >>> from pprint import pprint >>> >>> G = nx.DiGraph([(0, 1), (1, 2), (2, 1)]) >>> pprint(list(nx.dfs_labeled_edges(G, source=0))) [(0, 0, 'forward'), (0, 1, 'forward'), (1, 2, 'forward'), (2, 1, 'nontree'), (1, 2, 'reverse'), (0, 1, 'reverse'), (0, 0, 'reverse')] Notes ----- If a source is not specified then a source is chosen arbitrarily and repeatedly until all components in the graph are searched. The implementation of this function is adapted from David Eppstein's depth-first search function in `PADS`_, with modifications to allow depth limits based on the Wikipedia article "`Depth-limited search`_". .. _PADS: http://www.ics.uci.edu/~eppstein/PADS .. _Depth-limited search: https://en.wikipedia.org/wiki/Depth-limited_search See Also -------- dfs_edges dfs_preorder_nodes dfs_postorder_nodes Nr=r nontreer rr3r rr!r!r"r \sBA     r )NN) __doc__ collectionsrnetworkxr#__all__rrrrrrr r!r!r!r"s  Q - 2 5 33