#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
typedef long long ll;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
const int maxn = 2e5 + 10;
int n, a[maxn], used[maxn], pos[maxn];
vector < int > adj[maxn];
ll dp[maxn];
int rec(int val)
{
if (used[val])
return dp[val];
used[val] = 1;
int left = 0, right = n + 1;
for (int i = n; i > val; i --)
{
if (pos[i] > pos[val])
{
right = min(right, pos[i]);
}
else
{
left = max(left, pos[i]);
}
}
int mx = -1;
for (int i = pos[val] + 1; i < right; i ++)
{
if (a[i] > mx)
{
mx = a[i];
dp[val] = max(dp[val], (ll)(i - pos[val] + rec(a[i])));
}
}
mx = -1;
for (int i = pos[val] - 1; i > left; i --)
{
if (a[i] > mx)
{
mx = a[i];
dp[val] = max(dp[val], (ll)(pos[val] - i + rec(a[i])));
}
}
return dp[val];
}
int dfs(int v, int p, int mx, int dis, int val)
{
if (mx > val)
return 0;
int ans = 0;
if (a[v] == mx)
ans = max((ll)ans, dis + dp[v]);
for (int u : adj[v])
{
if (u == p)
continue;
ans = max(ans, dfs(u, v, max(mx, a[u]), dis + 1, val));
}
return ans;
}
int best[maxn], par[maxn], depth[maxn];
int tin[maxn], tout[maxn], timer, heavy[maxn];
int occ[2 * maxn], sub[maxn];
void trav(int v)
{
occ[++ timer] = v;
tin[v] = timer;
heavy[v] = -1;
sub[v] = 1;
for (int u : adj[v])
{
if (u == par[v])
continue;
depth[u] = depth[v] + 1;
par[u] = v;
trav(u);
sub[v] += sub[u];
if (heavy[v] == -1 || sub[heavy[u]] > sub[heavy[v]])
heavy[v] = u;
occ[++ timer] = v;
}
tout[v] = timer;
}
const int maxlog = 20;
int fp[maxlog][2 * maxn], lg[2 * maxn];
void build_sparse_table()
{
for (int i = 1; i <= timer; i ++)
{
lg[i] = lg[i / 2] + 1;
fp[0][i] = occ[i];
}
for (int j = 1; j < lg[timer]; j ++)
for (int i = 1; i <= timer - (1 << j) + 1; i ++)
{
fp[j][i] = fp[j - 1][i + (1 << (j - 1))];
if (depth[fp[j - 1][i]] < depth[fp[j][i]])
fp[j][i] = fp[j - 1][i];
}
}
int lca_query(int v, int u)
{
int l = tin[v], r = tin[u];
if (l > r)
swap(l, r);
int len = lg[r - l + 1] - 1, lca = fp[len][r - (1 << len) + 1];
if (depth[fp[len][l]] < depth[lca])
lca = fp[len][l];
return lca;
}
int distance(int v, int u)
{
return depth[v] + depth[u] - 2 * depth[lca_query(v, u)];
}
struct chain
{
int left, right, head;
chain()
{
left = 0;
right = 0;
head = 0;
}
} chains[maxn];
int chain_count, chain_idx[maxn], chain_pos[maxn];
int order[maxn];
void hld(int v)
{
chain_idx[v] = chain_count;
chain_pos[v] = ++ chains[chain_count].right;
order[chains[chain_count].right] = v;
if (heavy[v] != -1)
{
hld(heavy[v]);
}
for (int u : adj[v])
{
if (u == par[v] || u == heavy[v])
continue;
chain_count ++;
chains[chain_count].left = chains[chain_count - 1].right + 1;
chains[chain_count].right = chains[chain_count - 1].right;
chains[chain_count].head = u;
hld(u);
}
}
int tree[4 * maxn], lazy[4 * maxn];
void propagate(int root, int left, int right)
{
if (lazy[root] == 0)
return;
if (left != right)
{
tree[root * 2] = lazy[root];
tree[root * 2 + 1] = lazy[root];
lazy[root * 2] = lazy[root];
lazy[root * 2 + 1] = lazy[root];
}
lazy[root] = 0;
}
void update(int root, int left, int right, int qleft, int qright, int val)
{
if (left > qright || right < qleft)
return;
if (left >= qleft && right <= qright)
{
tree[root] = val;
lazy[root] = val;
return;
}
propagate(root, left, right);
int mid = (left + right) / 2;
update(root * 2, left, mid, qleft, qright, val);
update(root * 2 + 1, mid + 1, right, qleft, qright, val);
tree[root] = max(tree[root * 2], tree[root * 2 + 1]);
}
int query(int root, int left, int right, int qleft, int qright)
{
if (left > qright || right < qleft)
return 0;
if (left >= qleft && right <= qright)
return tree[root];
propagate(root, left, right);
int mid = (left + right) / 2;
return max(query(root * 2, left, mid, qleft, qright),
query(root * 2 + 1, mid + 1, right, qleft, qright));
}
int lead[maxn], lf_lead[maxn], rf_lead[maxn];
int find_leader(int v)
{
if (v == lead[v])
return v;
return (lead[v] = find_leader(lead[v]));
}
void unite(int v, int u)
{
v = find_leader(v);
u = find_leader(u);
if (v == u)
return;
lf_lead[v] = min(lf_lead[v], lf_lead[u]);
rf_lead[v] = max(rf_lead[v], rf_lead[u]);
lead[u] = v;
}
int active[maxn];
void solve()
{
cin >> n;
for (int i = 1; i <= n; i ++)
{
cin >> a[i];
pos[a[i]] = i;
}
bool chain = true;
for (int i = 1; i < n; i ++)
{
int v, u;
cin >> v >> u;
if (!(v == i && u == i + 1))
chain = false;
adj[v].push_back(u);
adj[u].push_back(v);
}
trav(1);
build_sparse_table();
timer = 0;
chain_count = 1;
chains[chain_count].left = 1;
chains[chain_count].right = 0;
chains[chain_count].head = 1;
hld(1);
/**for (int i = 1; i <= chain_count; i ++)
{
cout << "chain " << i << endl;
for (int j = chains[i].left; j <= chains[i].right; j ++)
cout << order[j] << " ";
cout << endl;
}*/
for (int i = 1; i <= n; i ++)
{
lf_lead[i] = rf_lead[i] = lead[i] = i;
}
for (int i = 1; i <= n; i ++)
{
int v = pos[i];
active[v] = 1;
//cout << "step" << endl;
//cout << v << endl;
for (int u : adj[v])
{
///cout << u << endl;
if (u == par[v])
continue;
///cout << "fine" << endl;
int cur = query(1, 1, n, chain_pos[u], chain_pos[u]);
///cout << chain_pos[u] << " : " << chain_pos[u] << endl;
if (cur != 0)
{
///cout << "check " << cur << endl;
dp[v] = max(dp[v], dp[pos[cur]] + distance(v, pos[cur]));
}
}
int cur_idx = chain_idx[v], cur_pos = chain_pos[v];
while(true)
{
if (a[order[cur_pos]] > i)
break;
int cur_lead = find_leader(cur_pos), lf = chains[cur_idx].left, rf = cur_pos;
lf = max(lf, lf_lead[cur_lead]);
int cur_best = query(1, 1, n, lf, rf);
///cout << "check " << cur_best << endl;
if (cur_best != 0)
dp[v] = max(dp[v], dp[pos[cur_best]] + distance(v, pos[cur_best]));
if (lf_lead[cur_lead] > chains[cur_idx].left || par[chains[cur_idx].head] == 0)
break;
cur_pos = chain_pos[par[chains[cur_idx].head]];
cur_idx = chain_idx[order[cur_pos]];
}
cur_idx = chain_idx[v];
cur_pos = chain_pos[v];
if (active[order[chain_pos[v] - 1]])
unite(order[chain_pos[v] - 1], v);
if (active[order[chain_pos[v] + 1]])
unite(order[chain_pos[v] + 1], v);
while(true)
{
if (a[order[cur_pos]] > i)
break;
int cur_lead = find_leader(cur_pos), lf = chains[cur_idx].left, rf = cur_pos;
lf = max(lf, lf_lead[cur_lead]);
update(1, 1, n, lf, rf, i);
///cout << "updated " << lf << " " << rf << endl;
if (lf_lead[cur_lead] > chains[cur_idx].left || par[chains[cur_idx].head] == 0)
break;
cur_pos = chain_pos[par[chains[cur_idx].head]];
cur_idx = chain_idx[order[cur_pos]];
}
//cout << "dp " << v << " " << dp[v] << endl;
}
cout << dp[pos[n]] << endl;
}
int main()
{
speed();
solve();
return 0;
}
/**
5
5 3 2 1 4
1 2
2 3
3 4
4 5
*/
Compilation message
Main.cpp: In function 'void solve()':
Main.cpp:254:10: warning: variable 'chain' set but not used [-Wunused-but-set-variable]
254 | bool chain = true;
| ^~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
7468 KB |
Output is correct |
| 2 |
Incorrect |
4 ms |
7508 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
7516 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
