运输计划noip

靠！这道题TM搞了我好几天，真是烦死人！！！早上打了一个倍增的TM只有95分QAQ。。。

然后一气之下开始不断卡常，各种玄学优化，可是就是T。。TAT。。

可恶！晚上我就直接打了个tarjan，还好跑过了，可是打的我身心俱残！！！仿佛想起了打splay的岁月，各个代码3000+。。。

不过一次就打成功了，还算比较好吧。。。

先上95分的代码

#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#define maxn 600500
#define ll long long 
using namespace std;
struct st{
    ll u,v,next,val;
}s[maxn];

struct qu{
    ll a,b,lca,len;
}quest[maxn];

ll n,m,u,v,root,tot,val,head[maxn],ceng[maxn],fa[maxn][20],len[maxn],fedge[maxn],zou[maxn],cf[maxn],maxlen,l,r,ma;

inline void add(ll u,ll v,ll val)
{
    tot++;
    s[tot].val = val;
    s[tot].u = u;
    s[tot].v = v;
    s[tot].next = head[u];
    head[u] = tot;
}

inline void dfs(ll f,ll now)
{
    fa[now][0] = f;
    ceng[now] = ceng[f] + 1;
    for(ll i = head[now];i;i = s[i].next)
    {
        v = s[i].v;
        if(!ceng[v])
        {
            fedge[v] = s[i].val;
            len[v] = len[now] + s[i].val;
            dfs(now,v);
        }
    }
}

inline void init()
{
    for(ll j=1;(1<<j)<=n;j++)
    {
        for(ll i=1;i<=n;i++)
        {
            fa[i][j]=fa[fa[i][j-1]][j-1];
        }
    }    
}

inline ll lca(ll a,ll b)
{
    if(ceng[a] > ceng[b]) swap(a,b);
    ll cha = ceng[b] - ceng[a];
    for(ll i = 0;(1 << i) <= cha;i++)
    {
        if((1 << i) & cha) b = fa[b][i];
    }
    if(a!=b)
    {
        for(ll i=(ll)log2(n);i>=0;i--)
        {
            if(fa[a][i]!=fa[b][i])
            {
                a=fa[a][i];
                b=fa[b][i];
            }
        }
        a = fa[a][0];
    }
    return a;
}

inline ll find(ll pos,ll num)
{
    ll val = cf[pos];
    zou[pos] = 1;
    for(ll i=head[pos];i;i=s[i].next)
    {
        if(zou[s[i].v]) continue;
        val += find(s[i].v,num);
    }
    if(val >= num) ma = max(ma,fedge[pos]);
    return val;
}

inline ll check(ll ans)
{
    memset(zou,0,sizeof(zou));
    memset(cf,0,sizeof(cf));
    ll ce = 0;
    for(ll i=1;i<=m;i++)
    {
        if(quest[i].len > ans)
        {
            cf[quest[i].a]++;
            cf[quest[i].b]++;
            cf[quest[i].lca] -= 2;
            ce++;
        }
    }
    ma = -1;
    find(1,ce);
    if(ma == -1) return 0;
    if(ans + ma >= maxlen) return 1;
    return 0;
}

int main(){
    scanf("%lld%lld%",&n,&m);
    for(ll i=1;i<n;i++)
    {
        scanf("%lld%lld%lld",&u,&v,&val);
        add(u,v,val);
        add(v,u,val);
    }
    
    dfs(0,1);
    init();
    for(ll i=1;i<=m;i++)
    {
        scanf("%lld%lld",&u,&v);
        quest[i].a = u;
        quest[i].b = v;
        quest[i].lca = lca(u,v);
        quest[i].len = len[u] + len[v] - 2 * len[quest[i].lca];
        maxlen = max(maxlen , quest[i].len);
    }
    r = maxlen;
    while(l < r)
    {
        ll mid = l + r >> 1;
        if(check(mid)) r = mid;
        else l = mid + 1;
    }
    printf("%lld",l);
} 

 然后上个100 的！！！

#include<cstdio>
#include<algorithm>
#define maxn 300300 << 1
using namespace std;
int head_edge[maxn],head_quest[maxn],fedge[maxn],f[maxn],len[maxn],vis[maxn],cf[maxn],n,m,ma,maxlen,tot,u,v,val,l,r;

struct st{
    int v,val,next;
}s[maxn];

struct que{
    int u,v,lca,len,next;
    que *es;
}quest[maxn];

inline int find(int x)
{
    if(f[x] == x) return x;
    f[x] = find(f[x]);
    return f[x];
}

inline void add_edge(int u,int v,int val)
{
    tot++;
    s[tot].v = v;
    s[tot].val = val;
    s[tot].next = head_edge[u];
    head_edge[u] = tot;
}

inline void add_quest(int u,int v)
{
    tot++;
    quest[tot].u = u;
    quest[tot].v = v;
    if(tot & 1)    quest[tot].es = &quest[tot + 1];
    else quest[tot].es = &quest[tot - 1];
    quest[tot].next = head_quest[u];
    head_quest[u] = tot;
}

inline void dfs_tarjan(int father,int now)
{
    for(int i=head_edge[now];i;i=s[i].next)
    {
        if(father == s[i].v) continue;
        fedge[s[i].v] = s[i].val;
        len[s[i].v] = len[now] + s[i].val;
        dfs_tarjan(now,s[i].v);
    }
}

inline void lca_tarjan(int father,int now)
{
    for(int i=head_edge[now];i;i=s[i].next)
    {
        if(s[i].v == father) continue;
        lca_tarjan(now,s[i].v);
    }
    for(int i=head_quest[now];i;i=quest[i].next)
    {
        if(vis[quest[i].v])
        {
            quest[i].lca = find(quest[i].v);
            quest[i].len = len[quest[i].u] + len[quest[i].v] - 2 * len[quest[i].lca];
            quest[i].es -> lca = quest[i].lca;
            quest[i].es -> len = quest[i].len;
            maxlen = max(maxlen,quest[i].len);
        }
    }
    vis[now] = 1;
    f[now] = father;
}

inline int dfs_check(int pos,int num)
{
    vis[pos] = 1;
    int val = cf[pos];
    for(int i=head_edge[pos];i;i=s[i].next)
    {
        if(vis[s[i].v]) continue;
        val += dfs_check(s[i].v,num);
    }
    if(val >= num) ma = max(ma,fedge[pos]);
    return val;
}

inline int check(int ans)
{
    for(int i=1;i<=n;i++)
    {
        vis[i] = 0;
        cf[i] = 0;
    }
    int num = 0;
    ma = -1;
    for(int i=1;i<=m;i++)
    {
        if(quest[i].len > ans)
        {
            cf[quest[i].u]++;
            cf[quest[i].v]++;
            cf[quest[i].lca] -= 2;
            num++;
        }
    }
    if(!num) return 1;
    dfs_check(1,num);
    if(ma == -1 || ans + ma < maxlen) return 0;
    return 1;
}

int main(){
    scanf("%d%d",&n,&m);
    
    for(int i=1;i<n;i++)
    {
        scanf("%d%d%d",&u,&v,&val);
        add_edge(u,v,val);
        add_edge(v,u,val);
    }
    dfs_tarjan(0,1);
    tot = 0;
    for(int i=1;i<=n;i++) f[i] = i;
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d",&u,&v);
        add_quest(u,v);
        add_quest(v,u);
    }
    
    lca_tarjan(0,1);
    for(int i=1;i<=m;i++) quest[i] = quest[i * 2];
    
    r = maxlen;
    l = max(0,r - 1000);
    while(l < r)
    {
        int mid = l + r >> 1;
        if(check(mid)) r = mid;
        else l = mid + 1;
    }
    printf("%d",l);
}