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;
}