Submission #75489

# Submission time Handle Problem Language Result Execution time Memory
75489 2018-09-09T23:06:40 Z qkxwsm Building Bridges (CEOI17_building) C++17
30 / 100
346 ms 4956 KB
/*
PROG: source
LANG: C++11
_____
.'     '.
/  0   0  \
|     ^     |
|  \     /  |
\  '---'  /
'._____.'
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;

struct chash
{
        int operator()(int x) const
        {
                x ^= (x >> 20) ^ (x >> 12);
                return x ^ (x >> 7) ^ (x >> 4);
        }
        int operator()(long long x) const
        {
                return x ^ (x >> 32);
        }
};

template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using hashtable = gp_hash_table<T, U, chash>;

template<class T>
void readi(T &x)
{
        T input = 0;
        bool negative = false;
        char c = ' ';
        while (c < '-')
        {
                c = getchar();
        }
        if (c == '-')
        {
                negative = true;
                c = getchar();
        }
        while (c >= '0')
        {
                input = input * 10 + (c - '0');
                c = getchar();
        }
        if (negative)
        {
                input = -input;
        }
        x = input;
}
template<class T>
void printi(T output)
{
        if (output == 0)
        {
                putchar('0');
                return;
        }
        if (output < 0)
        {
                putchar('-');
                output = -output;
        }
        int aout[20];
        int ilen = 0;
        while(output)
        {
                aout[ilen] = ((output % 10));
                output /= 10;
                ilen++;
        }
        for (int i = ilen - 1; i >= 0; i--)
        {
                putchar(aout[i] + '0');
        }
        return;
}
template<class T>
void ckmin(T &a, T b)
{
        a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
        a = max(a, b);
}
template<class T, class U>
T normalize(T x, U mod = 1000000007)
{
        return (((x % mod) + mod) % mod);
}
long long randomizell(long long mod)
{
        return ((1ll << 45) * rand() + (1ll << 30) * rand() + (1ll << 15) * rand() + rand()) % mod;
}
int randomize(int mod)
{
        return ((1ll << 15) * rand() + rand()) % mod;
}

#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define debug(x) cerr << #x << " = " << x << endl;

const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-10;

#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 100013

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;

int N;
pll arr[MAXN];
ll dp[MAXN];
ll pref[MAXN];
ordered_set<pll> chull;

ll overpass(pll x, pll y)
{
	ll m1 = x.fi, b1 = x.se, m2 = y.fi, b2 = y.se;
	//when does x beat y?
	if (m1 == m2)
	{
		if (b1 < b2) return -LLINF;
		else return LLINF;
	}
	//m1x + b1 < m2x + b2
	//(m2 - m1) x > (b1 - b2)
	//x >= (b1 - b2) / (m2 - m1)
	return (b1 - b2 + (m2 - m1 - 1)) / (m2 - m1);
}
void comb(ordered_set<pll> &a, pll x)
{
	if (a.empty())
	{
		a.insert(x);
		return;
	}
	// cerr << "insert " << x.fi << "x + " << x.se << endl;
	auto it = a.LB(x);
	if (*it == x || (prev(it)) -> fi == x.fi)
	{
		return;
	}
	if (it == a.end())
	{
		a.insert(x);
		return;
	}
	while(next(it) != a.end() && overpass(x, *it) <= overpass(*it, *next(it)))
	{
		it = a.erase(it);
	}
	if (it == a.begin())
	{
		while (it != a.end() && it -> fi == x.fi)
		{
			it = a.erase(it);
		}
		a.insert(x);
		return;
	}
	it--;
	while(it != a.begin() && overpass(*it, x) >= overpass(*prev(it), *it))
	{
		it = a.erase(it);
		it--;
	}
	if (a.empty() || x.fi < a.begin() -> fi || x.fi > a.rbegin() -> fi)
	{
		a.insert(x);
		return;
	}
	ll cx = overpass(*it, *next(it));
	if (x.fi * cx + x.se < (it -> fi) * cx + (it -> se) || x.fi * (cx - 1) + x.se < (next(it) -> fi) * (cx - 1) + (next(it) -> se))
	{
		a.insert(x);
	}
	return;
}
//take it to the left as
ll query(ll x, ordered_set<pll> &a)
{
	if (a.empty())
	{
		return 0ll;
	}
	int lo = 0, hi = a.size() - 1;
	while(hi > lo)
	{
		int mid = (lo + hi) / 2;
		pll pr = *a.find_by_order(mid), pl = *a.find_by_order(mid + 1);
		if (overpass(pr, pl) <= x)
		{
			hi = mid;
		}
		else
		{
			lo = mid + 1;
		}
	}
	pll opt = *a.find_by_order(lo);
	// cerr << "contains: ";
	// for (pll x : a)
	// {
	// 	cerr << x.fi << "x + " << x.se << endl;
	// }
	// cerr << "query " << x << " get " << opt.fi * x + opt.se << endl;
	return opt.fi * x + opt.se;
}
int32_t main()
{
        ios_base::sync_with_stdio(0);
        srand(time(0));
        //	cout << fixed << setprecision(10);
        //	cerr << fixed << setprecision(10);
        if (fopen("input.in", "r"))
        {
                freopen ("input.in", "r", stdin);
                freopen ("output.out", "w", stdout);
        }
        cin >> N;
        for (int i = 0; i < N; i++)
        {
                cin >> arr[i].fi;
        }
        for (int i = 0; i < N; i++)
        {
                cin >> arr[i].se;
        }
        for (int i = 0; i < N; i++)
        {
                pref[i + 1] = pref[i] + arr[i].se;
        }
        dp[0] = 0;
        for (int i = 0; i < N; i++)
        {
                if (i)
                {
                        // cerr << "query " << -2 * arr[i].fi << ' ' << query(-2 * arr[i].fi, chull) << endl;
                        dp[i] = query(-2 * arr[i].fi, chull) + (arr[i].fi * arr[i].fi + pref[i]);
                        // for (int j = 0; j < i; j++)
                        // {
                        //         //(arr[i] - arr[j])^2 = (arr[j]^2) - 2 * arr[i] * arr[j] + arr[i]^2
                        //         ckmin(dp[i], -2 * arr[i].fi * arr[j].fi + dp[j] + arr[j].fi * arr[j].fi - pref[j + 1]);
                        // }
                }
                pll cur = {arr[i].fi, dp[i] + arr[i].fi * arr[i].fi - pref[i + 1]};
                // cerr << "insert " << cur.fi << "x + " << cur.se << endl;
                comb(chull, cur);
				// cerr << "contents of chull:\n";
				// for (pll x : chull)
				// {
				// 	cerr << x.fi << "x + " << x.se << endl;
				// }
                // cerr << dp[i] << endl;
        }
        cout << dp[N - 1] << '\n';
        //	cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
        return 0;
}

Compilation message

building.cpp: In function 'int32_t main()':
building.cpp:250:25: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
                 freopen ("input.in", "r", stdin);
                 ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
building.cpp:251:25: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
                 freopen ("output.out", "w", stdout);
                 ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
# Verdict Execution time Memory Grader output
1 Correct 2 ms 376 KB Output is correct
2 Correct 2 ms 500 KB Output is correct
3 Incorrect 2 ms 500 KB Output isn't correct
4 Halted 0 ms 0 KB -
# Verdict Execution time Memory Grader output
1 Correct 232 ms 3836 KB Output is correct
2 Correct 228 ms 3836 KB Output is correct
3 Correct 230 ms 3836 KB Output is correct
4 Correct 193 ms 3836 KB Output is correct
5 Correct 346 ms 4956 KB Output is correct
# Verdict Execution time Memory Grader output
1 Correct 2 ms 376 KB Output is correct
2 Correct 2 ms 500 KB Output is correct
3 Incorrect 2 ms 500 KB Output isn't correct
4 Halted 0 ms 0 KB -