2016秋季练习

来源：lightOJ1011

MST+树链剖分

树剖写挫了RE一个晚上啊

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#define lson rt<<1
#define rson rt<<1|1
using namespace std;
int n,m,Q;
const int MAXN = 50010;
struct Edge{//Treelink
int nxt,to,w;
}edge[MAXN<<2];
struct Qnode{//MST
int u,v,w;
inline void input(){
scanf("%d%d%d",&u,&v,&w);
}
inline void get(int uu,int vv,int ww){
u = uu;
v = vv;
w = ww;
}
}qnode[MAXN<<2],act[MAXN<<2];
int nnn;
int cmp(Qnode a,Qnode b){
return a.w<b.w;
}
int head[MAXN],tot;
int sum[MAXN],fa[MAXN],son[MAXN],p[MAXN],dep[MAXN],fp[MAXN],top[MAXN],pos;
int gr[MAXN<<1];
struct Segment{
int l,r;
int val;
}tree[MAXN<<2];
inline void ini(){
memset(head,-1,sizeof head);
memset(son,-1,sizeof son);
tot = nnn = pos = 0;
}
inline void addedge(int u,int v,int w){
edge[tot].to = v;
edge[tot].nxt = head[u];
edge[tot].w = w;
head[u] = tot ++;
}
int Find(int x){
if(gr[x] == -1) return x;
else return gr[x] = Find(gr[x]);
}
void kruscal(){
memset(gr,-1,sizeof gr);
sort(qnode+1,qnode+1+m,cmp);
for(int i=1;i<=m;i++){
int u = qnode[i].u;
int v = qnode[i].v;
int w = qnode[i].w;
int f1 = Find(u);
int f2 = Find(v);
if(f1!=f2){
gr[f1] = f2;
addedge(u,v,w);
addedge(v,u,w);
act[++nnn].get(u,v,w);
}
}
}
void dfs(int rt,int pre,int d){
sum[rt] = 1;
fa[rt] = pre;
dep[rt] = d;
for(int i=head[rt];i!=-1;i=edge[i].nxt){
int now = edge[i].to;
if(now == pre) continue;
dfs(now,rt,d+1);
sum[rt] += sum[now];
if(son[rt] == -1 || sum[now]>sum[son[rt]]) {
son[rt] = now;
}
}
}
void getpos(int rt,int sp){
top[rt] = sp;
p[rt] = ++pos;
fp[p[rt]] = rt;
if(son[rt]==-1) return ;
getpos(son[rt],sp);
for(int i=head[rt];i!=-1;i=edge[i].nxt){
int now = edge[i].to;
if(now == fa[rt] || now == son[rt]) continue;
getpos(now,now);
}
}

inline void pushup(int rt){
tree[rt].val = max(tree[lson].val,tree[rson].val);
}
void build(int rt,int l,int r){
tree[rt].l = l;
tree[rt].r = r;
tree[rt].val = 0;
if(l == r) {
return ;
}
int mid = (l+r)>>1;
build(lson,l,mid);
build(rson,mid+1,r);
pushup(rt);
}
void update(int rt,int pos,int data){
if(tree[rt].l == pos && pos == tree[rt].r) {
tree[rt].val = data;
return ;
}
int mid = (tree[rt].l+tree[rt].r)>>1;
if(pos<=mid) update(lson,pos,data);
if(pos>=mid+1) update(rson,pos,data);
pushup(rt);
}
int query(int rt,int l,int r){
if(l<=tree[rt].l && tree[rt].r<=r){
return tree[rt].val;
}
int mid = (tree[rt].l+tree[rt].r)>>1;
if(r<=mid) return query(lson,l,r);
else if(l>mid) return query(rson,l,r);
else return max(query(lson,l,mid),query(rson,mid+1,r));
}
int solve(int u,int v){
int ans = -1;
int f1 = top[u];
int f2 = top[v];
while(f1!=f2){
if(dep[f1]<dep[f2]){
swap(f1,f2);
swap(u,v);
}
ans = max(ans,query(1,p[f1],p[u]));
u = fa[f1];
f1 = top[u];
}
if(u == v) return ans;
else if(dep[u]>dep[v]) swap(u,v);
ans = max(ans,query(1,p[son[u]],p[v]));
return ans;
}
int main(){
int T,nc = 1;
int u,v,w;
int l,r;
scanf("%d",&T);
while(T--){
ini();
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++){
qnode[i].input();
}
kruscal();
dfs(1,-1,0);
pos = 0;
getpos(1,1);
build(1,1,pos);
for(int i=1;i<=nnn;i++){
int u = act[i].u;
int v = act[i].v;
int cost = act[i].w;
if(dep[u]>dep[v]) swap(u,v);
update(1,p[v],cost);
}
printf("Case %d:\n",nc++);
scanf("%d",&Q);
while(Q--){
scanf("%d%d",&l,&r);
printf("%d\n",solve(l,r));
}
}
return 0;
}