Submission #1250788

#	Time	Username	Problem	Language	Result	Execution time	Memory
1250788		s4dz	Triple Peaks (IOI25_triples)	C++20	26 / 100	2096 ms	33096 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();
    long long count = 0;

    for (int i = 0; i < n; i++) {
        long long k = (long long)i + H[i];
        if (k < n) {
            if (H[i] > H[k]) {
                int diff = H[i] - H[k];
                int j1 = i + diff;
                int j2 = i + H[k];
                if (j1 > i && j1 < k && H[j1] == diff) {
                    count++;
                }
                if (j2 > i && j2 < k && j2 != j1 && H[j2] == diff) {
                    count++;
                }
            }
        }
    }

    for (int k = 0; k < n; k++) {
        long long i0 = (long long)k - H[k];
        if (i0 >= 0) {
            if (H[k] > H[i0]) {
                int diff = H[k] - H[i0];
                int j1 = i0 + H[i0];
                int j2 = k - H[i0];
                if (j1 > i0 && j1 < k && H[j1] == diff) {
                    count++;
                }
                if (j2 > i0 && j2 < k && j2 != j1 && H[j2] == diff) {
                    count++;
                }
            }
        }
    }

    int MAXS = 2 * n + 10;
    vector<vector<int>> list_A(MAXS + 1);
    vector<vector<int>> list_sum(MAXS + 1);

    for (int i = 0; i < n; i++) {
        long long s = (long long)i + H[i];
        if (s <= MAXS) {
            list_A[s].push_back(i);
        }
    }

    for (int k = 0; k < n; k++) {
        long long s = (long long)k + H[k];
        if (s <= MAXS) {
            list_sum[s].push_back(k);
        }
    }

    int B = sqrt(n);
    for (int j = 0; j < n; j++) {
        long long s = j;
        if (s <= MAXS) {
            for (int i : list_A[s]) {
                if (i < j) {
                    long long k_val = (long long)i + H[j];
                    if (k_val < n) {
                        if (H[j] > H[i] && H[k_val] == H[j] - H[i]) {
                            count++;
                        }
                    }
                }
            }
        }

        long long s0 = (long long)j + H[j];
        if (s0 > MAXS) continue;
        long long low_bound = max((long long)j + 1, (long long)H[j]);
        long long high_bound = min((long long)n - 1, (long long)j + H[j] - 1);
        if (low_bound > high_bound) continue;

        vector<int>& L = list_sum[s0];
        if (L.empty()) continue;

        if (L.size() <= (size_t)B) {
            for (int k_val : L) {
                if (k_val < low_bound) continue;
                if (k_val > high_bound) break;
                int i_val = k_val - H[j];
                if (H[i_val] == k_val - j) {
                    count++;
                }
            }
        } else {
            for (int k_val = low_bound; k_val <= high_bound; k_val++) {
                if (k_val + H[k_val] == s0) {
                    int i_val = k_val - H[j];
                    if (i_val >= 0 && i_val < j && H[i_val] == k_val - j) {
                        count++;
                    }
                }
            }
        }
    }

    return count;
}

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: 11 / 11
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• Subtask 6: 0 / 19
• Subtask 7: 5 / 5
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• Subtask 9: 5 / 5
• Subtask 10: 0 / 5
• Subtask 11: 0 / 5
• Subtask 12: 0 / 5