SPOJ 375

默默一看提交时间 ……

这是我以前的代码风格……

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
#define N 10005
#define lson(x) ((x<<1))
#define rson(x) ((x<<1)+1)
#define Del(a,b) memset(a,b,sizeof(a))
using namespace std;  

int dep[N],siz[N],fa[N],id[N],son[N],val[N],top[N];
int num;
vector<int> v[N];

struct tree {
    int x,y,val;
    void read()
	{
        scanf("%d%d%d",&x,&y,&val);
    }
}e[N];

void dfs1(int u, int f, int d)
{
    dep[u] = d;
    siz[u] = 1;
    son[u] = 0;
    fa[u] = f;
    for (int i = 0; i < v[u].size(); i++)
	{
        int ff = v[u][i];
        if (ff == f) continue;
        dfs1(ff, u, d + 1);
        siz[u] += siz[ff];
        if (siz[son[u]] < siz[ff])
            son[u] = ff;
    }
}
void dfs2(int u, int tp) {
    top[u] = tp;
    id[u] = ++num;
    if (son[u]) dfs2(son[u], tp);
    for (int i = 0; i < v[u].size(); i++) {
        int ff = v[u][i];
        if (ff == fa[u] || ff == son[u]) continue;
        dfs2(ff, ff);
    }
}  

struct Tree
{
    int l,r,val;
};
Tree tree[4*N];  

void pushup(int x)
{
    tree[x].val = max(tree[lson(x)].val, tree[rson(x)].val);
}  

void build(int l,int r,int v)
{
    tree[v].l=l;
    tree[v].r=r;
    if(l==r)
    {
        tree[v].val=val[l];
        return ;
    }
    int mid=(l+r)>>1;
    build(l,mid,v*2);
    build(mid+1,r,v*2+1);
    pushup(v);
}  

void update(int o,int v,int val)
{
    if(tree[o].l==tree[o].r)
    {
        tree[o].val = val;
        return ;
    }
    int mid = (tree[o].l+tree[o].r)/2;
    if(v<=mid)
        update(o*2,v,val);
    else
        update(o*2+1,v,val);
    pushup(o);
}

int query(int x,int l, int r)
{
    if (tree[x].l >= l && tree[x].r <= r)
	{
        return tree[x].val;
    }
    int mid = (tree[x].l + tree[x].r) / 2;
    int ans = 0;
    if (l <= mid) ans = max(ans, query(lson(x),l,r));
    if (r > mid) ans = max(ans, query(rson(x),l,r));
    return ans;
}  

int Yougth(int u, int v)
{
    int tp1=top[u],tp2=top[v];
    int ans=0;
    while (tp1!=tp2)
	{
        if (dep[tp1] < dep[tp2])
		{
            swap(tp1, tp2);
            swap(u,v);
        }
        ans=max(query(1,id[tp1],id[u]),ans);
        u=fa[tp1];
        tp1=top[u];
    }
    if(u==v)return ans;
    if(dep[u]>dep[v])swap(u, v);
    ans=max(query(1,id[son[u]],id[v]),ans);
    return ans;
}

void Clear(int n)
{
    for(int i=1;i<=n;i++)
        v[i].clear();
}  

int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        int n;
        scanf("%d",&n);
        for(int i=1;i<n;i++)
        {
            e[i].read();
            v[e[i].x].push_back(e[i].y);
            v[e[i].y].push_back(e[i].x);
        }
        num = 0;
        dfs1(1,0,1);
        dfs2(1,1);
        for (int i = 1; i < n; i++)
		{
            if (dep[e[i].x] < dep[e[i].y]) swap(e[i].x, e[i].y);
            val[id[e[i].x]]=e[i].val;
        }
        build(1,num,1);//构造线段树
        char s[200];
        while(~scanf("%s",&s)&&s[0]!='D')
        {
            int x,y;
            scanf("%d%d",&x,&y);
            if(s[0]=='Q')
                printf("%d\n",Yougth(x,y));
            if (s[0] == 'C')
                update(1,id[e[x].x],y);
        }
        Clear(n);
    }
    return 0;
}

好像不太对

#include <algorihtm>
#include <iostream>
#include <cstring>
#include <vector>
#include <cstdio>
#define N 100005
using namespace std;

void read(int &s){
    char ch=getchar();int f=1;
    for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;
    for(s=0;isdigit(ch);s=s*10+ch-'0',ch=getchar());
    s*=f;
}

int son[N],val[N],top[N];
int dep[N],siz[N];
int fa[N],id[N];
int num;

struct Edge{
    int u,v,nxt,val;
}e[N];

void AddEdge(int u,int v,int value){
    e[++tot].v=v;e[tot].nxt=head[u];
    head[u]=tot;e[tot].val=value;e[tot].u=u;
    e[++tot].v=u;e[tot].nxt=head[v];
    head[v]=tot;e[tot].val=value;e[tot].u=v;
}

void dfs1(int u,int f){
    dep[u]=dep[f]+1;int to;
    siz[u]=1;son[u]=0;fa[u]=f;
    for(int i=head[u];i;i=e[i],nxt){
        to=e[i].v;
        if(f=to)continue;
        dfs1(to,u);size[u]+=siz[to];
        if(siz[son[u]]<siz[to])son[u]=to;
    }
}

void dfs2(int u,int to){
    top[u]=to;id[u]=++num;int v;
    if(son[u])dfs(son[u],to);
    for(int i=head[u];i;i=e[i].nxt){
        int v=e[u].v;
        if(v==fa[u]||v==son[u])continue;
        dfs2(v,v);
    }
}

struct T{
    int l,r,val;
}t[N<<2];

void pushup(int x){
    t[x].val=max(t[x<<1].val,t[x<<1|1].val);
}

void build(int l,int r,int ret){
    t[ret].l=l;t[ret].r=r;
    if(l==r){
        t[ret].val=val[l];
        return ;
    }
    int mid=(l+r)>>1;
    build(l,mid,ret<<1);
    build(mid+1,r,ret<<1|1);
    pushup(ret);
}

void update(int ret,int pos,int val){
    if(t[ret].l==t[ret].r){
        t[ret].val=val;
        return;
    }
    int mid=(t[ret].l+t[ret].r)>>1;
    if(pos<=mid)update(ret<<1,pos,val);
    else update(ret<<1|1,pos,val);
    pushup(ret);
}

int query(int L,int R,int ret){
    if(t[ret].l>=l&&t[ret].r<=r)
        return t[ret].val;
    int mid=(t[ret].l+t[ret].r)>>1;
    int ans=0;
    if(L<=mid)ans=max(ans,query(ret<<1,L,R));
    if(R>mid)ans=max(ans,query(ret<<1|1,L,R));
    return ans;
}

int Youth(int u,int v){
    int t1=top[u],t2=top[v];
    int ans=0;
    while(t1!=t2){
        if(dep[t1]<dep[t2]){
            swap(t1,t2);
            swap(u,v);
        }
        ans=max(query(id[t1],id[u],1),ans);
        u=fa[t1];
        t1=top[u];
    }
    if(u==v)return ans;
    if(dep[u]>dep[v])swap(u,v);
    ans=max(query(id[son[u]],id[v],1),ans);
    return ans;
}

void Clear(int n){
    for(int i=1;i<=n;++i)
        head[i]=0;
    tot=0;
}

int main(){
    int T,a,b,c,;read(T);
    while(T--){
        int n;read(n);
        for(int i=1;i<n;++i){
            read(a),read(b),read(c);
            AddEdge(a,b,c);
        }
        num=0;
        dfs1(1,0,1);
        dfs2(1,1);
        for(int i=1;i/2<n;++i){
            if(dep[e[i].u]<dep[e[i].y])swap(e[i].x,e[i].y);
            val[id[e[i].u]]=e[i].val;
        }
        build(1,num,1);
        char s[200];
        while(~scanf("%s",&s)&&s[0]!='D'){
            int x,y;
            scanf("%d%d",&x,&y);
            if(s[0]=='Q')
                printf("%d\n",Youth(x,y));
            if(s[0]=='C')
                update(1,id[e[x].u],y);
        }
        Clear(n);
    }
    return 0;