【BZOJ5110】【CodePlus2017】Yazid 的新生舞会

【题目链接】

• 点击打开链接
  

【思路要点】

• 补档博客，无题解。

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN	2000005
template <typename T> void read(T &x) {
x = 0; int f = 1;
char c = getchar();
for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
x *= f;
}
struct Segment_Tree {
struct Node {
int lc, rc;
long long sum, len, add, cnt;
bool clear;
} a[MAXN];
int n, root, size;
void build(int root, int l, int r) {
a[root].len = r - l + 1;
if (l == r) return;
int mid = (l + r) / 2;
a[root].lc = ++size;
build(size, l, mid);
a[root].rc = ++size;
build(size, mid + 1, r);
}
void init(int x) {
n = x;
root = size = 0;
build(root, 0, 2 * n);
}
long long func(long long len) {
return len * (len - 1) / 2;
}
void pushdown(int root) {
if (a[root].clear) {
int tmp = a[root].lc;
a[tmp].add = 0;
a[tmp].sum = 0;
a[tmp].cnt = 0;
a[tmp].clear = true;
tmp = a[root].rc;
a[tmp].add = 0;
a[tmp].sum = 0;
a[tmp].cnt = 0;
a[tmp].clear = true;
a[root].clear = false;
}
if (a[root].add) {
int tmp = a[root].lc;
a[tmp].add += a[root].add;
a[tmp].sum += a[tmp].len * a[root].add;
tmp = a[root].rc;
a[tmp].add += a[root].add;
a[tmp].sum += a[tmp].len * a[root].add;
a[root].add = 0;
}
if (a[root].cnt) {
int tmp = a[root].lc;
a[tmp].cnt += a[root].cnt;
a[tmp].sum += func(a[tmp].len) * a[root].cnt;
tmp = a[root].rc;
a[tmp].cnt += a[root].cnt;
a[tmp].add += a[root].cnt * a[a[root].lc].len;
a[tmp].sum += func(a[tmp].len) * a[root].cnt + a[root].cnt * a[a[root].lc].len * a[tmp].len;
a[root].cnt = 0;
}
}
void update(int root) {
a[root].sum = a[a[root].lc].sum + a[a[root].rc].sum;
}
void ModifyCnt(int root, int l, int r, int ql, int qr, long long d, long long extra) {
if (l == ql && r == qr) {
a[root].cnt += d;
a[root].add += d * extra;
a[root].sum += func(a[root].len) * d + extra * d * a[root].len;
return;
}
pushdown(root);
int mid = (l + r) / 2, len = 0;
if (mid >= ql) ModifyCnt(a[root].lc, l, mid, ql, min(qr, mid), d, extra), len = min(qr, mid) - ql + 1;
if (mid + 1 <= qr) ModifyCnt(a[root].rc, mid + 1, r, max(mid + 1, ql), qr, d, extra + len);
update(root);
}
void ModifyAdd(int root, int l, int r, int ql, int qr, long long d) {
if (l == ql && r == qr) {
a[root].add += d;
a[root].sum += a[root].len * d;
return;
}
pushdown(root);
int mid = (l + r) / 2;
if (mid >= ql) ModifyAdd(a[root].lc, l, mid, ql, min(qr, mid), d);
if (mid + 1 <= qr) ModifyAdd(a[root].rc, mid + 1, r, max(mid + 1, ql), qr, d);
update(root);
}
void modify(int l, int r, int d) {
if (l > r) return;
l += n, r += n;
ModifyCnt(root, 0, 2 * n, l, r, d, 0);
ModifyAdd(root, 0, 2 * n, r + 1, 2 * n, (r - l + 1) * d);
}
long long query(int root, int l, int r, int ql, int qr) {
if (l == ql && r == qr) return a[root].sum;
pushdown(root);
long long ans = 0;
int mid = (l + r) / 2;
if (ql <= mid) ans += query(a[root].lc, l, mid, ql, min(mid, qr));
if (qr >= mid + 1) ans += query(a[root].rc, mid + 1, r, max(mid + 1, ql), qr);
return ans;
}
long long query(int l, int r) {
if (l > r) return 0;
l += n, r += n;
return query(root, 0, 2 * n, l, r);
}
void clear() {
a[root].add = 0;
a[root].cnt = 0;
a[root].sum = 0;
a[root].clear = true;
}
} SGT;
vector <int> a[MAXN];
int n, type;
int main() {
read(n), read(type);
for (int i = 0; i <= n - 1; i++)
a[i].push_back(0);
int value = 0;
for (int i = 1; i <= n; i++) {
int x; read(x);
a[x].push_back(i);
value = max(value, x);
}
for (int i = 0; i <= value; i++)
a[i].push_back(n + 1);
SGT.init(n);
long long ans = 0;
for (int i = 0; i <= value; i++) {
SGT.modify(-a[i][1] + 1, 0, 1);
for (unsigned j = 1; j <= a[i].size() - 2; j++) {
int tmp = -a[i][j] + 2 * j;
ans += SGT.query(tmp, tmp);
SGT.modify(tmp, tmp, 1);
ans += SGT.query(tmp - (a[i][j + 1] - a[i][j]) + 1, tmp - 1);
SGT.modify(tmp - (a[i][j + 1] - a[i][j]) + 1, tmp - 1, 1);
}
SGT.clear();
}
cout << ans << endl;
return 0;
}

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