SPOJ

给一棵树
修改边权和询问路径上的最大边权

树链剖分

把每条重链变成一条线段
然后用线段树来记录每条线段

查询的时候再用lca的方法往上走直到到达同一条重链

#include <iostream>#include <algorithm>#include <sstream>#include <string>#include <queue>#include <cstdio>#include <map>#include <set>#include <utility>#include <stack>#include <cstring>#include <cmath>#include <vector>#include <ctime>#include <bitset>using namespace std;#define pb push_back#define sd(n) scanf("%d",&n)#define sdd(n,m) scanf("%d%d",&n,&m)#define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k)#define sld(n) scanf("%lld",&n)#define sldd(n,m) scanf("%lld%lld",&n,&m)#define slddd(n,m,k) scanf("%lld%lld%lld",&n,&m,&k)#define sf(n) scanf("%lf",&n)#define sff(n,m) scanf("%lf%lf",&n,&m)#define sfff(n,m,k) scanf("%lf%lf%lf",&n,&m,&k)#define ss(str) scanf("%s",str)#define ansn() printf("%d\n",ans)#define lansn() printf("%lld\n",ans)#define r0(i,n) for(int i=0;i<(n);++i)#define r1(i,e) for(int i=1;i<=e;++i)#define rn(i,e) for(int i=e;i>=1;--i)#define mst(abc,bca) memset(abc,bca,sizeof abc)#define lowbit(a) (a&(-a))#define all(a) a.begin(),a.end()#define pii pair<int,int>#define mp(aa,bb) make_pair(aa,bb)#define lrt rt<<1#define rrt rt<<1|1#define X first#define Y second#define PI (acos(-1.0))typedef long long ll;typedef unsigned long long ull;const ll mod = 1000000000+7;const double eps=1e-9;const int inf=0x3f3f3f3f;//const ll infl = 10000000000000000;const int maxn=  10000+10;const int maxm = 1000+10;//Pretests passedint in(int &ret){    char c;    int sgn ;    if(c=getchar(),c==EOF)return -1;    while(c!='-'&&(c<'0'||c>'9'))c=getchar();    sgn = (c=='-')?-1:1;    ret = (c=='-')?0:(c-'0');    while(c=getchar(),c>='0'&&c<='9')ret = ret*10+(c-'0');    ret *=sgn;    return 1;}vector<int>g[maxn];int son[maxn],sz[maxn],fa[maxn],dep[maxn];int id[maxn], top[maxn];int dclock;void dfs1(int u,int f){    son[u] = 0;    sz[u] = 1;    fa[u] = f;    dep[u] = dep[f] + 1;    for(int i= 0 ; i<g[u].size(); ++i)    {        int v = g[u][i];        if(v==f)continue;        dfs1(v,u);        if(sz[son[u]]<sz[v])son[u] =v;        sz[u]+=sz[v];    }}void dfs2(int u,int f){    id[u] = ++dclock;    top[u] = f;    if(son[u]!=0)dfs2(son[u],top[u]);    int s = g[u].size();    for(int i =0 ; i<s; ++i)    {        int v = g[u][i];        if(v==fa[u]||v==son[u])continue;        dfs2(v,v);    }}int seg[maxn<<3];int n;void update(int rt,int l,int r,int p,int v){    if(l==r)    {        seg[rt] = v;        return;    }    int mid = (l+r)>>1;    if(p<=mid)update(lrt,l,mid,p,v);    else update(rrt,mid+1,r,p,v);    seg[rt] = max(seg[lrt],seg[rrt]);}int query(int rt,int l,int r,int ql,int qr){    if(ql<=l&&qr>=r)return seg[rt];    int mx = -inf;    int mid = (l+r)>>1;    if(ql<=mid)mx = max(mx,query(lrt,l,mid,ql,qr));    if(qr>mid)mx = max(mx,query(rrt,mid+1,r,ql,qr));    return mx;}int lca(int a,int b){    int ans = -inf;    while(top[a]!=top[b])    {        if(dep[top[a]]<dep[top[b]])swap(a,b);        ans = max(ans,query(1,2,n,id[top[a]],id[a]));        a = fa[top[a]];    }    if(dep[a]>dep[b])swap(a,b);    if(a!=b)ans = max(ans,query(1,2,n,id[a]+1,id[b]));    return ans;}int u[maxn],v[maxn],w[maxn];int main(){#ifdef LOCAL    freopen("input.txt","r",stdin);//    freopen("output.txt","w",stdout);#endif // LOCAL    int t;    sd(t);    while(t--)    {//        int n;        sd(n);        r1(i,n)g[i].clear();        r1(i,n-1)        {            int a,b,c;            sddd(a,b,c);            u[i] = a;            v[i] = b;            w[i] = c;            g[a].pb(b);            g[b].pb(a);        }        dclock  = 0;        dfs1(1,0);        fa[1] = 1;        dfs2(1,1);        mst(seg,0xc0);//        printf("%d",seg[0]);        r1(i,n-1)        {            int &a = u[i], &b = v[i];            if(dep[a]<dep[b])swap(a,b);            update(1,2,n,id[a],w[i]);        }        while(1)        {            char s[30];            ss(s);            if(s[0]=='D')break;            if(s[0]=='Q')            {                int a,b;                sdd(a,b);                int ans = lca(a,b);                ansn();            }            else            {                int a,b;                sdd(a,b);                update(1,2,n,id[u[a]],b);            }        }    }    return 0;}