Submission #1249808

#	Time	Username	Problem	Language	Result	Execution time	Memory
1249808		QwertyPi	Triple Peaks (IOI25_triples)	C++20	21.69 / 100	1624 ms	16000 KiB

triples

#include "triples.h"
#include <bits/stdc++.h>

#define int long long

using namespace std;

const int N_MAX = 2e5 + 11;
int N;
int H[N_MAX];

bool in(int x) {
    return 0 <= x && x < N;
}

bool check(int a, int b, int c) {
    if (!in(a) || !in(b) || !in(c) || a >= b || b >= c) return false;
    return multiset<int>{H[a], H[b], H[c]} == multiset<int>{abs(a - b), abs(a - c), abs(b - c)};
}

int ans = 0;
set<tuple<int, int, int>> S;

bool check_set(int a, int b, int c) {
    bool ok = check(a, b, c);
    if (!ok) return false;
    if (S.count({a, b, c})) return false;
    S.insert({a, b, c}); ans++; return true;
}

int count_triples(vector<int32_t> H) {
    N = H.size();
    for (int i = 0; i < N; i++) ::H[i] = H[i];

    for (int i = 0; i < N; i++) {
        int a = i;
        {
            int b = a - H[a];
            if (in(b)) {
                int c = b + H[b];
                check_set(b, a, c);
            }
            if (in(b)) {
                int c = a + H[b];
                check_set(b, a, c);
            }
        }

        {
            int b = a + H[a];
            if (in(b)) {
                int c = b - H[b];
                check_set(c, a, b);
            }
            if (in(b)) {
                int c = a - H[b];
                check_set(c, a, b);
            }
        }
    }

    for (int a = 0; a < N; a++) {
        for (int c = a + 2; c < a + 30; c++) {
            check_set(a, a + H[a], c);
            check_set(a, a + H[c], c);
        }
    }
    return ans;
}

vector<int32_t> construct_range(int32_t M, int32_t _K) {

    const int K = sqrt(M);
    M = M / K * K - 1;
    vector<int32_t> ans(M);
    int B = M / K;
    for (int i = 0; i < B; i++) {
        for (int j = 0; j < K; j++) {
            ans[i * K + j] = K * (B - 1 - i) + 1 + j;
        }
    }
    for (int j = 0; j < K - 1; j++) {
        ans[B * K + j] = K - 1 - j;
    }
    // cout << "ANS = " << count_triples(ans) << endl;
    return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 0 / 8
• Subtask 2: 6 / 6
• Subtask 3: 0 / 10
• Subtask 4: 11 / 11
• Subtask 5: 0 / 16
• Subtask 6: 0 / 19
• Subtask 7: 2.5 / 5
• Subtask 8: 1.1525 / 5
• Subtask 9: 0.4901 / 5
• Subtask 10: 0.2113 / 5
• Subtask 11: 0.2488 / 5
• Subtask 12: 0.0829 / 5