Submission #473730

#	Time	Username	Problem	Language	Result	Execution time	Memory
473730		Lam_lai_cuoc_doi	Bigger segments (IZhO19_segments)	C++17	100 / 100	98 ms	12920 KiB

segments

#define task "PARTITION"

#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>

using namespace std;

using ll = long long;
using ld = long double;

template <class T>
void read(T &x)
{
    x = 0;
    register int c;
    while ((c = getchar()) && (c > '9' || c < '0'))
        ;
    for (; c >= '0' && c <= '9'; c = getchar())
        x = x * 10 + c - '0';
}

constexpr int N = 5e5 + 5;
constexpr int Inf = 1e9 + 7;
int n, pre[N], ans[N];
ll a[N];

void Read()
{
    cin >> n;
    //read(n);
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    //read(a[i]);
    //reverse(a + 1, a + n + 1);

    for (int i = 1; i <= n; ++i)
        a[i] += a[i - 1];
}

void Sub_1()
{
    vector<vector<int>> dp(n + 5, vector<int>(n + 5, -Inf));

    dp[0][0] = 0;

    for (int i = 1; i <= n; ++i)
    {
        for (int j = i - 1, t = i - 2; j >= 0; --j)
        {
            if (t >= j)
                --t;
            while (t >= 0 && a[i] - a[j] >= a[j] - a[t])
                --t;
            dp[i][j] = max(dp[i][j + 1], dp[j][t + 1] + 1);
        }
    }

    cout << dp[n][0];
}

void Greedy()
{
    for (int i = 1; i <= n; ++i)
    {
        pre[i] = max(pre[i], pre[i - 1]);

        ans[i] = ans[pre[i]] + 1;

        int j = lower_bound(a + 1, a + n + 1, a[i] * 2 - a[pre[i]]) - a;

        pre[j] = max(pre[j], i);
    }

    cout << ans[n];
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen(task ".INP", "r"))
    {
        freopen(task ".INP", "r", stdin);
        freopen(task ".OUT", "w", stdout);
    }
    Read();
    if (n <= 1000)
        Sub_1();
    else
        Greedy();
}

Compilation message (stderr)

segments.cpp: In function 'void read(T&)':
segments.cpp:17:18: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
   17 |     register int c;
      |                  ^
segments.cpp: In function 'int32_t main()':
segments.cpp:86:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   86 |         freopen(task ".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
segments.cpp:87:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   87 |         freopen(task ".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 14 / 14
• Subtask 3: 10 / 10
• Subtask 4: 36 / 36
• Subtask 5: 27 / 27