如何在不违反O（| V | + | E |）的情况下在dfs树中存储节点级别

Question

有没有办法在它所属的DFS树中存储每个顶点的级别？

时间复杂度应为O(|V| + |E|)。

Answer 1

这是来自wikipedia的标准DFS伪代码：

1  procedure DFS(G,v):
2      label v as discovered
3      for all edges from v to w in G.adjacentEdges(v) do
4          if vertex w is not labeled as discovered then
5              recursively call DFS(G,w)

添加级别：

1  procedure DFS(G,v,level):
2      label v as discovered
3      v.level = level
4      for all edges from v to w in G.adjacentEdges(v) do
5          if vertex w is not labeled as discovered then
6              recursively call DFS(G,w,level+1)

首先致电DFS(G,v,0)