HDU 2586 + HDU 4912 最近公共祖先

#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#define max(x,y) ((x)>(y)?(x):(y))
#define NN 200002 // number of house
using namespace std;

int be[NN],all,ans;
bool vis2[NN],vis3[NN];

typedef struct node{
int v;
int d;
struct node *nxt;
}NODE;

struct edge{
int u,v,ne;
}e[NN];

NODE *Link1[NN];
NODE edg1[NN * 2];

NODE *Link2[NN];
NODE edg2[NN * 2];

int idx1, idx2, N, M;
int res[NN][3];
int fat[NN];
int vis[NN];
int dis[NN];

void Add(int u, int v, int d, NODE edg[], NODE *Link[], int &idx){
edg[idx].v = v;
edg[idx].d = d;
edg[idx].nxt = Link[u];
Link[u] = edg + idx++;

edg[idx].v = u;
edg[idx].d = d;
edg[idx].nxt = Link[v];
Link[v] = edg + idx++;
}

int find(int x){
if(x != fat[x]){
return fat[x] = find(fat[x]);
}
return x;
}

void Tarjan(int u){
vis[u] = 1;
fat[u] = u;

for (NODE *p = Link2[u]; p; p = p->nxt){
if(vis[p->v]){
res[p->d][2] = find(p->v);
}
}

for (NODE *p = Link1[u]; p; p = p->nxt){
if(!vis[p->v]){
dis[p->v] = dis[u] + p->d;
Tarjan(p->v);
fat[p->v] = u;
}
}
}

void add(int fa,int x,int y)
{
++all;
e[all].u=x;
e[all].v=y;
e[all].ne=be[fa];
be[fa]=all;
}

void color(int u)
{
for (NODE *p = Link1[u]; p; p = p->nxt)
if(vis3[p->v] && !vis2[p->v])
{
vis2[p->v]=1;
color(p->v);
}
}

void dfs(int u)
{
vis[u]=1;
for (NODE *p = Link1[u]; p; p = p->nxt)
if(!vis[p->v])    dfs(p->v);

for (int i=be[u]; i!=-1; i=e[i].ne)
if(!vis2[e[i].u] && !vis2[e[i].v])
{
vis2[u]=1;
ans++;
color(u);
}
vis3[u]=1;

}

int main() {
int T, i, u, v, d;
while(scanf("%d%d", &N, &M)!=EOF)
{
idx1 = 0;
memset(Link1, 0, sizeof(Link1));
for (i = 1; i < N; i++){
scanf("%d%d", &u, &v);
d=0;
Add(u, v, d, edg1, Link1, idx1);
}

idx2 = 0;
memset(Link2, 0, sizeof(Link2));
for (i = 1; i <= M; i++){
scanf("%d%d", &u, &v);
Add(u, v, i, edg2, Link2, idx2);
res[i][0] = u;
res[i][1] = v;
}

memset(vis, 0, sizeof(vis));
dis[1] = 0;
Tarjan(1);

all=0;
memset(be,-1,sizeof(be));
memset(vis,0,sizeof(vis));
memset(vis2,0,sizeof(vis2));
memset(vis3,0,sizeof(vis3));
for(int i=1;i<=M; i++)
add(res[i][2],res[i][0],res[i][1]);
for(int i=1; i<=N; i++)
fat[i]=i;
ans=0;
dfs(1);
printf("%d\n",ans);
}
return 0;
}