Submission #1262388

#	Time	Username	Problem	Language	Result	Execution time	Memory
1262388		Canuc80k	Triple Peaks (IOI25_triples)	C++20	0 / 100	49 ms	31804 KiB

triples

#include "bits/stdc++.h"
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

ll res = 0;

void add(ll i, ll j, ll k) {res ++;}

inline ll packKey(int x, int y) {
    return ( (ll)(uint32_t)x << 32 ) | (uint32_t)y;
}

ll count(vector<int> a, vector<int> b) {
    int n = (int)a.size();
    if (n == 0) return 0;

    unordered_map<ll, int> cntPair;
    cntPair.reserve(n * 2);
    for (int i = 0; i < n; ++i) {
        cntPair[ packKey(a[i], b[i]) ] += 1;
    }

    unordered_map<int, vector<pair<int,int>>> listA;
    listA.reserve(cntPair.size());
    for (auto &it : cntPair) {
        ll key = it.first;
        int freq = it.second;
        int x = (int)(key >> 32);
        int y = (int)(key & 0xffffffff);
        listA[x].push_back({y, freq});
    }

    auto getCnt = [&](int x, int v)->int {
        ll key = packKey(x, v);
        auto it = cntPair.find(key);
        if (it == cntPair.end()) return 0;
        return it->second;
    };

    ll total = 0;
    for (auto &it : cntPair) {
        ll key = it.first;
        int f_xy = it.second;
        int x = (int)(key >> 32);
        int y = (int)(key & 0xffffffff);

        auto itLy = listA.find(y);
        if (itLy == listA.end()) continue;
        auto &Lx = listA[x];
        auto &Ly = itLy->second;

        ll dot = 0;
        if (Lx.size() <= Ly.size()) {
            for (auto &p : Lx) {
                int v = p.first;
                int cxv = p.second;
                int cyv = getCnt(y, v);
                if (cyv) dot += (ll)cxv * cyv;
            }
        } else {
            for (auto &p : Ly) {
                int v = p.first;
                int cyv = p.second;
                int cxv = getCnt(x, v);
                if (cxv) dot += (ll)cxv * cyv;
            }
        }
        total += (ll)f_xy * dot;
    }
    return total;
}

long long count_triples(std::vector<int> H) {
    // #TH: a[k] max
    for (int k = 2; k < H.size(); k ++) {
        int i = k - H[k]; if (i < 0 || H[i] >= H[k]) continue; int j1 = k - H[i], j2 = i + H[i];
        if (j1 < 0 || H[j1] >= H[k] || H[j1] != j1 - i) j1 = -1;
        if (j2 >= k || H[j2] >= H[k] || H[j2] != k - j2) j2 = -1;
        if (j1 != -1) add(i, j1, k); if (j2 != -1 && j1 != j2) add(i, j2, k);
    }

    // #TH: a[i] max
    for (int i = 0; i + 2 < H.size(); i ++) {
        int k = i + H[i]; if (k >= H.size() || H[k] >= H[i]) continue; int j1 = k - H[k], j2 = i + H[k];
        if (j1 < 0 || H[j1] >= H[i] || H[j1] != j1 - i) j1 = -1;
        if (j2 >= k || H[j2] >= H[i] || H[j2] != k - j2) j2 = -1;
        if (j1 != -1) add(i, j1, k); if (j2 != -1 && j1 != j2) add(i, j2, k);
    }
    
    // #TH: a[j] max, j - i = a[i]
    for (int i = 0; i + 2 < H.size(); i ++) {
        int j = i + H[i]; if (j >= H.size() || H[j] <= H[i]) continue; int k = i + H[j];
        if (k >= H.size() || H[k] >= H[j] || k - H[k] != j || k - j == H[i]) k = -1;
        if (k != -1) add(i, j, k);
    }

    // #TH: a[j] max, j - i = a[k]
    vector<int> a, b;
    for (int i = 0; i < H.size(); i ++) a.push_back(H[i] + i);
    for (int i = 0; i < H.size(); i ++) b.push_back(H[i] - i);
    res += count(a, b);
    return res;
}

std::vector<int> construct_range(int M, int K) {
    // vector<int> res; res.push_back(1);
    // for (int i = 1; i < M; i ++) res.push_back(i);
    // return res;
}

Compilation message (stderr)

triples.cpp: In function 'std::vector<int> construct_range(int, int)':
triples.cpp:111:1: warning: no return statement in function returning non-void [-Wreturn-type]
  111 | }
      | ^

• 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: 0 / 5
• Subtask 8: 0 / 5
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• Subtask 10: 0 / 5
• Subtask 11: 0 / 5
• Subtask 12: 0 / 5