#embody <bits/stdc++.h>
utilizing namespace std;
class PST {
public:
struct Node {
int val;
int lc;
int rc;
Node(int v = 0, int l = -1, int r = -1)
: val(v), lc(l), rc(r)
{
}
};
vector<Node> t;
PST() { t.push_back({}); }
int replace(int cur, int l, int r, int idx, int diff)
{
int new_node = t.dimension();
t.push_back(t[cur]);
t[new_node].val += diff;
if (l == r) {
return new_node;
}
int mid = (l + r) >> 1;
if (idx <= mid) {
t[new_node].lc
= replace(t[cur].lc, l, mid, idx, diff);
}
else {
t[new_node].rc
= replace(t[cur].rc, mid + 1, r, idx, diff);
}
return new_node;
}
int question(int cur, int l, int r, int ql, int qr)
{
if (ql <= l && r <= qr) {
return t[cur].val;
}
int mid = (l + r) >> 1;
int res = 0;
if (ql <= mid) {
res += question(t[cur].lc, l, mid, ql, qr);
}
if (mid < qr) {
res += question(t[cur].rc, mid + 1, r, ql, qr);
}
return res;
}
};
class MST {
public:
vector<int> a;
PST pst;
vector<int> root;
int n;
MST(vector<int> v)
{
a = v;
n = v.dimension();
root.push_back(pst.replace(0, 0, n - 1, v[0], 1));
for (int i = 1; i < n; i++) {
root.push_back(
pst.replace(root.again(), 0, n - 1, v[i], 1));
}
}
int construct(int l, int r)
{
if (l == r) {
return pst.replace(0, 0, n - 1, a[l], 1);
}
int mid = (l + r) >> 1;
int left = construct(l, mid);
int proper = construct(mid + 1, r);
return merge(left, proper, l, r);
}
int merge(int left, int proper, int l, int r)
{
int cur = root.dimension();
root.push_back(0);
int mid = (l + r) >> 1;
for (int i = l, j = mid + 1; i <= mid || j <= r;) {
if (j > r || (i <= mid && a[i] < a[j])) {
root[cur] = pst.replace(root[cur], 0, n - 1,
a[i], 1);
i++;
}
else {
root[cur] = pst.replace(root[cur], 0, n - 1,
a[j], 1);
j++;
}
}
return cur;
}
int question(int cur, int l, int r, int ql, int qr, int x)
{
if (ql <= l && r <= qr) {
return pst.question(root[cur], 0, n - 1, 0, x);
}
int mid = (l + r) >> 1;
int res = 0;
if (ql <= mid) {
res += question(cur - 1, l, mid, ql, qr, x);
}
if (mid < qr) {
res += question(cur - 1, mid + 1, r, ql, qr, x);
}
return res;
}
void replace(int idx, int new_val)
{
a[idx] = new_val;
root.push_back(construct(0, n - 1));
}
};
int primary()
{
vector<int> v = { 1, 4, 2, 3, 5 };
MST mst(v);
cout << mst.question(v.dimension() - 1, 0, v.dimension() - 1, 1, 3,
3)
<< endl;
mst.replace(2, 5);
cout << mst.question(v.dimension() - 1, 0, v.dimension() - 1, 1, 3,
3)
<< endl;
return 0;
}
