結果

問題 No.1300 Sum of Inversions
コンテスト
ユーザー kaikey
提出日時 2020-11-28 00:22:29
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
WA  
実行時間 -
コード長 6,685 bytes
コンパイル時間 2,496 ms
コンパイル使用メモリ 210,864 KB
最終ジャッジ日時 2025-01-16 08:51:01
ジャッジサーバーID
（参考情報） 		judge1 / judge1
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 2 WA * 32
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include <bits/stdc++.h>
#include <random>
using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef pair<lint, lint> plint; typedef pair<double long, double long> pld;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define endk '\n'
template<class T> auto add = [](T a, T b) -> T { return a + b; };
template<class T> auto f_max = [](T a, T b) -> T { return max(a, b); };
template<class T> auto f_min = [](T a, T b) -> T { return min(a, b); };
template<class T> using V = vector<T>;
using Vl = V<lint>; using VVl = V<Vl>;
template< typename T > ostream& operator<<(ostream & os, const vector< T > & v) {
    for (int i = 0; i < (int)v.size(); i++) os << v[i] << (i + 1 != v.size() ? " " : "");
    return os;
}
template< typename T >istream& operator>>(istream & is, vector< T > & v) {
    for (T& in : v) is >> in;
    return is;
}
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); }
lint ceil(lint a, lint b) { return (a + b - 1) / b; }
lint digit(lint a) { return (lint)log10(a); }
lint dist(plint a, plint b) { return abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second); }
void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); }
const lint MOD = 1e9 + 7, INF = 5e18;
lint dx[8] = { 1, 0, -1, 0, 1, -1, 1, -1 }, dy[8] = { 0, 1, 0, -1, -1, -1, 1, 1 };
void YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; } void yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; }
typedef pair<lint, string> Pa;
typedef pair<lint, plint> tlint;
struct Edge {
    lint from, to;
	lint cost;
	Edge(lint u, lint v, lint c) {
		cost = c;
		from = u;
		to = v;
	}
    bool operator<(const Edge& e) const {
        return cost < e.cost;
    }
};
struct WeightedEdge {
	lint to;
    lint cost;
	WeightedEdge(lint v, lint c = 1) {
		to = v;
		cost = c;
	}
    bool operator<(const WeightedEdge& e) const {
        return cost < e.cost;
    }
};
using WeightedGraph = V<V<WeightedEdge>>;


template <std::int_fast64_t Modulus>
class modint
{
	using u64 = std::int_fast64_t;

public:
	u64 a;
	constexpr modint(const u64 x = 0) noexcept : a(x% Modulus) {}
	constexpr u64& value() noexcept { return a; }
	constexpr const u64& value() const noexcept { return a; }
	constexpr modint operator+(const modint rhs) const noexcept
	{
		return modint(*this) += rhs;
	}
	constexpr modint operator-(const modint rhs) const noexcept
	{
		return modint(*this) -= rhs;
	}
	constexpr modint operator*(const modint rhs) const noexcept
	{
		return modint(*this) *= rhs;
	}
	constexpr modint operator/(const modint rhs) const noexcept
	{
		return modint(*this) /= rhs;
	}
	constexpr modint& operator+=(const modint rhs) noexcept
	{
		a += rhs.a;
		if (a >= Modulus)
		{
			a -= Modulus;
		}
		return *this;
	}
	constexpr modint& operator-=(const modint rhs) noexcept
	{
		if (a < rhs.a)
		{
			a += Modulus;
		}
		a -= rhs.a;
		return *this;
	}
	constexpr modint& operator*=(const modint rhs) noexcept
	{
		a = a * rhs.a % Modulus;
		return *this;
	}
	constexpr modint& operator/=(modint rhs) noexcept
	{
		u64 exp = Modulus - 2;
		while (exp)
		{
			if (exp % 2)
			{
				*this *= rhs;
			}
			rhs *= rhs;
			exp /= 2;
		}
		return *this;
	}
};
typedef modint<MOD> ModInt;

ModInt mod_pow(ModInt x, lint n) {
	ModInt ret = 1;
	while (n > 0) {
		if (n & 1) (ret *= x);
		(x *= x);
		n >>= 1;
	}
	return ret;
}

ModInt func[200000];
void funcinit(int N)
{
	func[0] = 1;
	for (int i = 1; i <= N; i++)
	{
		func[i] = func[i - 1] * i;
	}
}
ModInt comb(ModInt n, ModInt r)
{
	if (n.a <= 0 || n.a < r.a)
	{
		return 1;
	}
	return func[n.a] / (func[r.a] * func[(n - r).a]);
}

struct BinaryIndexedTree {
	int n;
	vector<lint> bit;
	BinaryIndexedTree(int n_) : n(n_ + 1), bit(n, 0) {}
	void add(int i, lint x) {
		for (int idx = i; idx < n; idx += (idx & -idx)) {
			bit[idx] += x;
		}
	}
	lint sum(int i) {
		lint s = 0;
		for (int idx = i; idx > 0; idx -= (idx & -idx)) {
			s += bit[idx];
		}
		return s;
	}
	int lower_bound(lint w) {
		if (w <= 0) {
			return 0;
		}
		else {
			int x = 0, r = 1;
			while (r < n) r = r << 1;
			for (int len = r; len > 0; len = len >> 1) {
				if (x + len < n && bit[x + len] < w) {
					w -= bit[x + len];
					x += len;
				}
			}
			return x;
		}
	}
	void show() {
		for (int i = 0; i < n - 1; i++) {
			cout << sum(i) - sum(i - 1) << " ";
		}
		cout << endk;
	}
};

struct ExtendBinaryIndexedTree {
public:
	ExtendBinaryIndexedTree(int _n) { init(_n); }
	//半開区間[l, r)
	void add(int l, int r, lint x) {
		add_sub(0, l, -x * (l - 1));
		add_sub(0, r, x * (r - 1));
		add_sub(1, l, x);
		add_sub(1, r, -x);
	}
	//区間[0, i)
	lint sum(int i) {
		return sum_sub(0, i) + sum_sub(1, i) * i;
	}

	void show() {
		for (int i = 0; i < n - 1; i++) {
			cout << sum(i + 1) - sum(i) << " ";
		}
		cout << endk;
	}
private:
	int n;
	vector<lint> bit[2];
	void init(int _n) {
		n = _n + 1;
		bit[0].assign(n, 0);
		bit[1].assign(n, 0);
	}
	void add_sub(int p, int i, lint x) {
		for (int idx = i; idx < n; idx += (idx & -idx)) {
			bit[p][idx] += x;
		}
	}
	lint sum_sub(int p, int i) {
		lint s = 0;
		for (int idx = i; idx > 0; idx -= (idx & -idx)) {
			s += bit[p][idx];
		}
		return s;
	}
};



lint N;
int main() {
    cin.tie(0); ios_base::sync_with_stdio(false);
    cin >> N;
	vector<lint> arr(N);
	set<lint> st;
	REP(i, N) {
		cin >> arr[i];
		st.insert(arr[i]);
	}
	vector<lint> vec;
	vec.push_back(0);
	for (lint v : st) vec.push_back(v);
	map<lint, lint> fx;
	for (int i = 0; i < SZ(vec); i++) {
		fx[vec[i]] = i;
	}
	REP(i, N) {
		arr[i] = fx[arr[i]];
	}
	BinaryIndexedTree upper_sum(SZ(vec)), lower_sum(SZ(vec));
	BinaryIndexedTree upper_tree(SZ(vec)), lower_tree(SZ(vec));
	REP(i, N) {
		lower_sum.add(arr[i], vec[arr[i]]);
		lower_tree.add(arr[i], 1);
	}
	ModInt ans = 0;
	REP(i, N) {
		lower_sum.add(arr[i], -vec[arr[i]]);
		lower_tree.add(arr[i], -1);
		ModInt l = lower_tree.sum(arr[i] - 1), u = upper_tree.sum(SZ(vec)) - upper_tree.sum(arr[i]);
		ans += u * lower_sum.sum(arr[i] - 1);
		ans += u * l * vec[arr[i]];
		ans += l * (upper_sum.sum(SZ(vec)) - upper_sum.sum(arr[i]));
		upper_sum.add(arr[i], vec[arr[i]]);
		upper_tree.add(arr[i], 1);
	}
	cout << ans.a << endk;
}
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