Submission #1250798

#	Time	Username	Problem	Language	Result	Execution time	Memory
1250798		s4dz	Triple Peaks (IOI25_triples)	C++20	15 / 100	2095 ms	32444 KiB

triples

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
//sub4:
vector<int> construct_range(int M, int K) {
    vector<int> ans1 = {
        4,  3,  1,  2,  1,
        4,  3,  2,  7,  6,
        5,  8, 11, 10,  9,
        1,  7,  2,  3,  4,
    };

    if(M <= 20){
        while(ans1.size() > M || ans1.back() >= M) ans1.pop_back();
        return ans1;
    }
    vector<int> S = {0};
    vector<bool> in_span(2*M, false);
    int span_cnt = 0;
    vector<pair<int,int>> pts;

    while(span_cnt < M-1) {
        int best_t = -1, best_gain = -1;
        vector<bool> inS(2*M, false);
        for(int u:S) inS[u] = true;
        for(int t = 0; t <= 2*(M-1); t += 2) if(!inS[t]) {
            int gain = 0;
            for(int u:S) {
                if(u==t) continue;
                int s = u + t;
                if(s >= 2 && s <= 2*(M-1) && (s%2==0) && !in_span[s]) ++gain;
            }
            if(gain > best_gain) {
                best_gain = gain;
                best_t = t;
            }
        }
        if(best_t < 0) break;
        for(int u:S) {
            if(u == best_t) continue;
            int s = u + best_t;
            if(s >= 2 && s <= 2*(M-1) && (s%2==0) && !in_span[s]) {
                int x = min(u, best_t), y = max(u, best_t);
                pts.emplace_back(x, y);
                in_span[s] = true;
                ++span_cnt;
            }
        }
        S.push_back(best_t);
    }
    vector<int> H(M, 1);
    for(auto [x,y] : pts) {
        int idx = (x + y) / 2;
        int h   = (y - x) / 2;
        if(idx >= 0 && idx < M) {
            H[idx] = h;
        }
    }
    return H;
}
/*long long count_triples(vector<int> H)
{
    int n = H.size();
    ll ans = 0;
    for (int k = 0; k < n; k++)
    {
        int c = H[k];
        int i = k - c;
        if (i < 0 || i >= n) continue;

        int a = H[i];
        if (a > c - a) continue;

        int need = c - a;
        int j1   = i + a;
        int j2   = k - a;
        if (i < j1 && j1 < k && H[j1] == need) ans++;
        if (j2 != j1 && i < j2 && j2 < k && H[j2] == need) ans++;
    }
    return ans;
}*/
/*void nen(vector<int>& H)
{
    vector<int> temp = H;
    sort(temp)
}*/
long long count_thdb(vector<signed> H)
{
    int n = H.size();
    vector<int> u(n), v(n);
    for(int i = 0; i < n; i++)
    {
        u[i] = i - H[i];
        v[i] = i + H[i];
    }

}
long long count_triples(vector<int> H) {
    int n = H.size();
    vector<vector<int>> list_by_A(n + 1);
    vector<vector<int>> list_by_B(n + 1);

    for (int j = 0; j < n; j++) {
        int a = j - H[j];
        if (a >= 0 && a < n) {
            list_by_A[a].push_back(j);
        }
        int b = j + H[j];
        if (b < n) {
            list_by_B[b].push_back(j);
        }
    }

    long long count1 = 0;
    for (int i = 0; i < n; i++) {
        int k0 = i + H[i];
        if (k0 >= n) continue;

        for (int j : list_by_A[i]) {
            if (i < j && j < k0) {
                if (H[k0] == k0 - j) {
                    count1++;
                }
            }
        }

        for (int j : list_by_B[k0]) {
            if (i < j && j < k0) {
                if (H[k0] == j - i) {
                    count1++;
                }
            }
        }
    }

    long long count21 = 0;
    for (int j = 0; j < n; j++) {
        for (int i : list_by_B[j]) {
            int k0 = i + H[j];
            if (k0 < n && k0 > j) {
                if (k0 - H[k0] == j) {
                    count21++;
                }
            }
        }
    }

    long long count22 = 0;
    unordered_map<int, vector<int>> groups;
    for (int i = 0; i < n; i++) {
        int x = H[i] - i;
        groups[x].push_back(i);
    }
    for (auto &p : groups) {
        auto &list_i = p.second;
        sort(list_i.begin(), list_i.end());
        int n_list = list_i.size();
        for (int i_idx = 0; i_idx < n_list; i_idx++) {
            for (int j_idx = i_idx + 1; j_idx < n_list; j_idx++) {
                int i1 = list_i[i_idx];
                int i2 = list_i[j_idx];
                int d = i2 - i1;
                int k = i1 + H[i2];
                if (k < 0 || k >= n) continue;
                if (H[k] == d) {
                    count22++;
                }
            }
        }
    }

    long long count3 = 0;
    for (int j = 0; j < n; j++) {
        int k0 = j + H[j];
        if (k0 >= n) continue;
        for (int i : list_by_B[j]) {
            if (H[k0] == H[i] + H[j]) {
                count3++;
            }
        }
    }
    for (int j = 0; j < n; j++) {
        int i0 = j - H[j];
        if (i0 < 0 || i0 >= j) continue;
        int k0 = j + H[i0];
        if (k0 < n && k0 > j) {
            if (H[k0] == H[i0] + H[j]) {
                count3++;
            }
        }
    }

    return count1 + count21 + count22 + count3;
}

Compilation message (stderr)

triples.cpp: In function 'long long int count_thdb(std::vector<int>)':
triples.cpp:97:1: warning: no return statement in function returning non-void [-Wreturn-type]
   97 | }
      | ^

• Subtask 0: 0 / 0
• Subtask 1: 0 / 8
• Subtask 2: 0 / 6
• Subtask 3: 0 / 10
• Subtask 4: 0 / 11
• Subtask 5: 0 / 16
• Subtask 6: 0 / 19
• Subtask 7: 5 / 5
• Subtask 8: 5 / 5
• Subtask 9: 5 / 5
• Subtask 10: 0 / 5
• Subtask 11: 0 / 5
• Subtask 12: 0 / 5