Created
October 5, 2022 18:26
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struct SegmentTree { | |
vector<ll> t; | |
int n; | |
inline ll ops(ll a, ll b) {return max(a,b);} | |
SegmentTree(vector<ll> &a) { | |
n = a.size(); | |
t.resize(2*n); | |
for (int i = 0; i < n; i++) | |
t[n + i] = a[i]; | |
for (int i = n - 1; i >= 1; i--) | |
t[i] = ops(t[2 * i],t[2 * i + 1]); | |
} | |
void update(int p, ll value) | |
{ | |
for (t[p += n] = value; p > 1; p >>= 1) t[p>>1] = ops(t[p] , t[p^1]); | |
} | |
ll get( int l, int r) | |
{ | |
ll res = LLONG_MIN; | |
for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) { | |
if (l&1) res = ops(res, t[l++]); | |
if (r&1) res = ops(t[--r], res); | |
} | |
return res; | |
} | |
}; | |
const int MAX = 2e5 + 7; | |
const int inf = 1e9 + 7; | |
int sz[MAX],in[MAX],rin[MAX],out[MAX],head[MAX],par[MAX]; | |
vector<int>g[MAX]; | |
vector<ll> tmp(10); | |
SegmentTree Tree(tmp); | |
void dfs_sz(int u,int p) { | |
sz[u] = 1; | |
par[u] = p; | |
for(auto &v: g[u]) { | |
if(v==p)continue; | |
dfs_sz(v,u); | |
sz[u] += sz[v]; | |
if(sz[v] > sz[g[u][0]]) | |
swap(v,g[u][0]); | |
} | |
} | |
int t = 0; | |
void dfs_hld(int u,int p) { | |
in[u] = ++t; | |
rin[in[u]] = u; | |
for(auto v: g[u]) { | |
if(v==p)continue; | |
head[v] = (v == g[u][0] ? head[u] : v); | |
dfs_hld(v,u); | |
} | |
out[u] = t; | |
} | |
bool isParent(int p,int u){ | |
return in[p]<=in[u]&&out[u]<=out[p]; | |
} | |
int n ; | |
int pathQuery(int u,int v){ | |
ll ret = -inf; | |
for (int i=0; i<2; i++) { | |
while(true){ | |
if(isParent(head[u],v))break; | |
ret=max(ret,Tree.get(in[head[u]],in[u]) ); | |
u=par[head[u]]; | |
} | |
swap(u,v); | |
} | |
if(in[v]<in[u])swap(u,v); | |
ret = max(ret,Tree.get(in[u],in[v])); | |
return ret; | |
} | |
void updateSubTree(int u,int val){ | |
Tree.update(in[u], val);//use lazy for subtree | |
} | |
void buildHLD(int root){ | |
dfs_sz(root,root); | |
head[root]=root; | |
dfs_hld(root,root); | |
} |
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