Submission #628051

#	Time	Username	Problem	Language	Result	Execution time	Memory
628051		bojackduy	Bigger segments (IZhO19_segments)	C++14	0 / 100	0 ms	212 KiB

segments

#include <bits/stdc++.h>

using namespace std;
typedef vector<int> vi;
typedef long long ll;
const int N = 1e6 + 1;
int n, res;
int a[N];
void iuq(int i, ll lst_sum , ll sum, int cnt) {
    if (i == n + 1) return void (res = max(res, cnt));
    if (i < n) iuq(i + 1, lst_sum, sum + a[i], cnt);
    if (lst_sum <= sum) {
        iuq(i + 1, sum, a[i], cnt + 1);
    }
}
void subtask1() {
    iuq(1, 0, 0, 0);
    cout << res;
}
void subtask2() {
    vector<vi> dp(n + 1, vi(n + 1, -1e9));
    for (int i = 1; i <= n; i++) dp[i][0] = 1;
    vector<ll> pre(n + 1, 0);
    for (int i = 1; i <= n; i++) pre[i] = pre[i - 1] + a[i];
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= i; j++) {
            for (int k = 1; k < j; k++) {
                int sum2 = pre[i] - pre[j - 1];
                int sum1 = pre[j - 1] - pre[k - 1];
                if (sum1 <= sum2) {
                    dp[i][j - 1] = max(dp[i][j - 1], dp[j - 1][k - 1] + 1);
                }
            }
        }
    }
    cout << *max_element(dp[n].begin(), dp[n].end());
}
struct IT {
    int n;
    vi st;
    IT(const int &_n = 0): n(_n), st(4 * _n + 1, -1e9) {}
    void adj(int id, int l, int r, int i, int val) {
        if (r < i || i < l) return ;
        if (l == r) return void (st[id] = val);
        int mid = l + r >> 1;
        adj(id << 1, l, mid, i, val);
        adj(id << 1 | 1, mid + 1, r, i, val);
        st[id] = max(st[id << 1], st[id << 1 | 1]);
    }
    void adj(int i, int val) {
        adj(1, 0, n, i, val);
    }
    int  get(int id, int l, int r, int u, int v) {
        if (r < u || v < l) return -1e9;
        if (u <= l && r <= v) return st[id];
        int mid = l + r >> 1;
    return max(get(id << 1, l, mid, u, v), get(id << 1 | 1, mid + 1, r, u, v));
    }
    int get(int u, int v) {
        return get(1, 0, n, u, v);
    }
};
void subtask3() {
    vector<vi> dp(n + 1, vi(n + 1, -1e9));
    vector<IT> it;
    it.resize(n + 1);
    for (int i = 0; i <= n; i++) it[i] = IT(n);
    dp[0][0] = 0;
    it[0].adj(0, 0);
    vector<ll> pre(n + 1, 0);
    for (int i = 1; i <= n; i++) pre[i] = pre[i - 1] + a[i];
    for (int i = 1; i <= n; i++) {
        int k = 1;
        for (int j = 1; j <= i; j++) {
            int sum = pre[i] - pre[j - 1];
            while (pre[j - 1] - pre[k - 1] > sum) k++;
            if (k <= j) {
                int cmax = it[j - 1].get(k - 1, j - 1);
                dp[i][j - 1] = cmax + 1;
                it[i].adj(j - 1, cmax + 1);
            }
        }
    }
    cout << *max_element(dp[n].begin(), dp[n].end());
}
int32_t main() {
    ios_base::sync_with_stdio(0);cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    if (n <= 20) {
        subtask1();
    return 0;
    }
    if (n <= 500) {
        subtask2();
    return 0;
    }
    subtask3();
    return 0;
}

Compilation message (stderr)

segments.cpp: In member function 'void IT::adj(int, int, int, int, int)':
segments.cpp:45:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   45 |         int mid = l + r >> 1;
      |                   ~~^~~
segments.cpp: In member function 'int IT::get(int, int, int, int, int)':
segments.cpp:56:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   56 |         int mid = l + r >> 1;
      |                   ~~^~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 14
• Subtask 3: 0 / 10
• Subtask 4: 0 / 36
• Subtask 5: 0 / 27