Submission #1249688

#	Time	Username	Problem	Language	Result	Execution time	Memory
1249688		QwertyPi	Triple Peaks (IOI25_triples)	C++20	19.65 / 100	1569 ms	15940 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) {
    // cout << a << ' ' << b << ' ' << c << endl;
    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) {
    if (M % 2 == 0) --M;
    vector<int32_t> A(M);
    int K = M / 2;
    for (int i = 0; i < K; i++) {
        A[i] = K - i;
        A[M - 1 - i] = K - i;
    }
    A[K] = K + 1;
    return A;
}

• 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: 1.5 / 5
• Subtask 8: 0.6225 / 5
• Subtask 9: 0.2499 / 5
• Subtask 10: 0.1071 / 5
• Subtask 11: 0.125 / 5
• Subtask 12: 0.0417 / 5