Lazy big pigeon $ HellPix $ to more Bo.
$ Tarjan $ three kinds of use:
- The strongly connected component: $ dfn [x] = low [x] $, the elements in the stack pop, pop until $ x $. Two-point reduction to become a $ DAG $, application: $ dp $ shrink point
- Undirected graph component by double Unicom: $ low [v]> = dfn [u] $, the elements in the stack pop, pop until $ $ V (At this time, also belong to this $ u $ double point, but because $ u $ is also possible to belong to another double points, so should remain in the $ u $ stack)
- Undirected edges bis Unicom component map: $ low [v]> dfn [u] $, then $ (u, v) $ as a cutting edge, $ dfn [x] = low pop (private thought when [x] $, no is equivalent to a dual edge has FIG), bis cissing become strongly points to a tree of FIG.