POJ 3352 Road Construction (conclusion of adding a double connected graph with the least side construction edge)

Test instructions: Known undirected graph, ask to add the least edge to make it a side double connected graph

Idea: It is obvious to indent the point into a tree, add the least side to make the edge of a tree connected

Here is the conclusion: for a tree to add (1+leaf) >>1 strip without the edge can be structured into a double-connected graph, the construction method is obvious (brain repair

    216k63msc++1754b #include <cstdio> #include <iostream> #include <cstring> #include <alg    Orithm> using namespace std;    const int N = 1010;    struct node {int v,next;    }es[n*n];    int head[n];    int n,m;    int low[n],dfn[n],index;    int indeg[n];        void Ini () {memset (head,-1,sizeof (head));        memset (dfn,0,sizeof (DFN));        index=0;    memset (indeg,0,sizeof (indeg));        } void Tarjan (int u,int pa) {dfn[u]=low[u]=++index;            for (int i=head[u];~i;i=es[i].next) {int v=es[i].v;                if (dfn[v]==0) {Tarjan (v,u);            Low[u]=min (Low[u],low[v]);        } if (V!=PA) low[u]=min (Low[u],low[v]);            }} int main () {while (~scanf ("%d%d", &n,&m)) {ini ();                for (int i=1;i<=m;i++) {int u,v;                scanf ("%d%d", &u,&v); ES[i].v=v;                Es[i].next=head[u];                Head[u]=i;                Es[i+m].v=u;                ES[I+M].NEXT=HEAD[V];            Head[v]=i+m;            } for (int i=1;i<=n;i++) if (dfn[i]==0) Tarjan (i,-1);                    for (int u=1;u<=n;u++) {for (int i=head[u];~i;i=es[i].next) {                    int v= es[i].v;                    if (Low[v]==low[u]) continue;                indeg[low[u]]++;            }} int leaf=0;            for (int i=1;i<=n;i++) if (indeg[i]==1) leaf++;        printf ("%d\n", (leaf+1)/2);    } return 0; }

POJ 3352 Road Construction (conclusion of adding a double connected graph with the least side construction edge)