Submission #1253442

#	Time	Username	Problem	Language	Result	Execution time	Memory
1253442		fve5	Triple Peaks (IOI25_triples)	C++20	16.29 / 100	75 ms	27588 KiB

triples

#include <bits/stdc++.h>
#include "triples.h"
using namespace std;

typedef long long i64;

i64 count_triples(vector<int> H) {
    auto check = [&](int i, int j, int k) {
        array<int, 3> h = {H[i], H[j], H[k]};
        array<int, 3> d = {abs(i - j), abs(i - k), abs(j - k)};
        sort(h.begin(), h.end());
        sort(d.begin(), d.end());
        return h == d;
    };

    int N = H.size();
    i64 ans = 0;

    for (auto _: {0, 1}) {
        for (int i = 0; i < N; i++) {
            int j = i + H[i];
            if (j >= N) continue;
            
            int k1 = j - H[j];
            if (k1 >= 0 && k1 > i) {
                ans += check(i, j, k1);
            }

            int k2 = i + H[j];
            if (k2 < N && k2 < j && k2 != k1) {
                ans += check(i, j, k2);
            }
        } 
        reverse(H.begin(), H.end());
    }

    vector<vector<int>> upds(N);
    for (int i = 0; i < N; i++) {
        upds[i].push_back(-H[i]);
        upds[max(i - H[i] + 1, 0)].push_back(H[i]);
    }

    vector<int> len_good_count(N);

    vector<vector<int>> by_diff(2 * N);
    for (int i = 0; i < N; i++)
        by_diff[i - H[i] + N].push_back(i);

    for (int i = 0; i < N; i++) {
        for (auto x: upds[i]) {
            if (x > 0) len_good_count[x]++;
            else len_good_count[-x]--;
        }

        if (i + H[i] >= N) continue;
        for (auto x: by_diff[i + H[i] + N])
            if (x > i)
                ans += len_good_count[x - i];
    }

    return ans;
}

vector<int> construct_range(int M, int K) {
    vector<int> A(M);
    iota(A.begin(), A.end(), 0);
    A[0] = 1;
    return A;
}

• Subtask 0: 0 / 0
• Subtask 1: 0 / 8
• Subtask 2: 0 / 6
• Subtask 3: 0 / 10
• Subtask 4: 11 / 11
• Subtask 5: 0 / 16
• Subtask 6: 0 / 19
• Subtask 7: 3 / 5
• Subtask 8: 1.245 / 5
• Subtask 9: 0.4998 / 5
• Subtask 10: 0.2143 / 5
• Subtask 11: 0.25 / 5
• Subtask 12: 0.0833 / 5