Submission #1121002

#	Time	Username	Problem	Language	Result	Execution time	Memory
1121002		steveonalex	Index (COCI21_index)	C++17	110 / 110	507 ms	138008 KiB

index

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()

ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}

ll gcd(ll a, ll b){return __gcd(a, b);}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ll mask){return __builtin_ctzll(mask);}
int logOf(ll mask){return __lg(mask);}

mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}

template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }

template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }

template <class T>
    void printArr(T& container, string separator = " ", string finish = "\n"){
        for(auto item: container) cout << item << separator;
        cout << finish;
    }


template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }struct Node {
    int cnt;
    Node *left, *right;
    Node() : cnt(0), left(nullptr), right(nullptr) {}
};

const int MAXN = 2e5 + 5;  // Adjust size as needed
const int MAXV = 2e5 + 5;  // Maximum value in the array

Node* roots[MAXN]; // Store version roots
vector<int> sortedArr; // Sorted version of the array for coordinate compression

// Build the initial segment tree
Node* build(int l, int r) {
    Node* node = new Node();
    if (l == r) return node; // Leaf node
    int mid = (l + r + 1) / 2;
    node->left = build(l, mid-1);
    node->right = build(mid, r);
    return node;
}

// Update the segment tree for a specific index
Node* update(Node* prev, int l, int r, int idx) {
    Node* node = new Node();
    if (l == r) {
        node->cnt = prev->cnt + 1; // Increment count
        return node;
    }
    int mid = (l + r + 1) / 2;
    if (idx < mid) {
        node->left = update(prev->left, l, mid - 1, idx);
        node->right = prev->right;
    } else {
        node->left = prev->left;
        node->right = update(prev->right, mid, r, idx);
    }
    node->cnt = node->left->cnt + node->right->cnt;
    return node;
}

// Query for the largest k where the count of numbers >= k is >= k
int findLargestK(Node* lRoot, Node* rRoot, int l, int r, int k) {
    if (l == r) {
        int count = rRoot->cnt - lRoot->cnt + k;
        if (count < l) assert(false);
        return l;
    }
    int mid = (l + r + 1) / 2;
    int countRight = rRoot->right->cnt - lRoot->right->cnt;
    // cout << mid << " " << r << " " << countRight << "\n";

    // Check if the solution lies in the right subtree
    if (countRight + k >= mid) {
        return findLargestK(lRoot->right, rRoot->right, mid, r, k);
    } else {
        return findLargestK(lRoot->left, rRoot->left, l, mid - 1, countRight + k);
    }
}

void solve() {
    int n, q; cin >> n >> q;
    vector<int> arr(n);
    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
        sortedArr.push_back(i + 1);
    }

    // Coordinate compression
    sort(sortedArr.begin(), sortedArr.end());
    sortedArr.erase(unique(sortedArr.begin(), sortedArr.end()), sortedArr.end());
    for (int i = 0; i < n; ++i) {
        arr[i] = lower_bound(sortedArr.begin(), sortedArr.end(), arr[i]) - sortedArr.begin() + 1;
    }

    // Build the persistent segment tree
    roots[0] = build(1, sortedArr.size());
    for (int i = 1; i <= n; ++i) {
        roots[i] = update(roots[i - 1], 1, sortedArr.size(), arr[i - 1]);
    }

    // Answer queries
    while (q--) {
        int l, r; cin >> l >> r;
        cout << findLargestK(roots[l - 1], roots[r], 1, sortedArr.size(), 0) << "\n";
    }
}
int main(void){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    clock_t start = clock();
    
    solve();

    cerr << "Time elapsed: " << clock() - start << "ms!\n";
    return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 40 / 40
• Subtask 3: 50 / 50