Submission #754640

#	Time	Username	Problem	Language	Result	Execution time	Memory
754640		boris_mihov	Radio Towers (IOI22_towers)	C++17	35 / 100	1507 ms	52708 KiB

towers

#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>
#include <stack>

typedef long long llong;
const int MAXLOG = 20 + 5;
const int MAXN = 100000 + 10;
const int INF  = 1e9;

int n;
struct MST
{
    std::vector <int> tree[4*MAXN];
    void build(int l, int r, int node, int vals[])
    {
        if (l == r)
        {
            tree[node].push_back(vals[l]);
            return;
        }

        int mid = (l + r) / 2;
        build(l, mid, 2*node, vals);
        build(mid + 1, r, 2*node + 1, vals);
        tree[node].reserve(r - l + 1);

        int lPtr = 0, rPtr = 0;
        for (int i = l ; i <= r ; ++i)
        {
            if (lPtr == tree[2*node].size())
            {
                tree[node].push_back(tree[2*node + 1][rPtr++]);
                continue;
            }

            if (rPtr == tree[2*node + 1].size())
            {
                tree[node].push_back(tree[2*node][lPtr++]);
                continue;
            }

            if (tree[2*node][lPtr] < tree[2*node + 1][rPtr])
            {
                tree[node].push_back(tree[2*node][lPtr++]);
            } else
            {
                tree[node].push_back(tree[2*node + 1][rPtr++]);
            }
        }
    }

    int binary(int node, int val)
    {
        int l = -1, r = tree[node].size(), mid;
        while (l < r - 1)
        {
            mid = (l + r) / 2;
            if (tree[node][mid] < val) l = mid;
            else r = mid;
        }

        return r;
    }

    int query(int l, int r, int node, int queryL, int queryR, int queryVal)
    {
        if (queryL <= l && r <= queryR)
        {
            return binary(node, queryVal);
        }

        int res = 0;
        int mid = (l + r) / 2;
        if (queryL <= mid) res += query(l, mid, 2*node, queryL, queryR, queryVal);
        if (mid + 1 <= queryR) res += query(mid + 1, r, 2*node + 1, queryL, queryR, queryVal);
        return res;
    }

    void build(int vals[])
    {
        build(1, n, 1, vals);
    }

    int query(int l, int r, int val)
    {
        return query(1, n, 1, l, r, val);
    }
};

MST left, right;
struct Sparse
{
    int sparse[MAXLOG][MAXN];
    int vals[MAXN];
    int lg[MAXN];

    int cmp(int x, int y)
    {
        if (vals[x] > vals[y]) return x;
        return y;
    }

    void build(int _vals[])
    {
        for (int i = 1 ; i <= n ; ++i)
        {
            sparse[0][i] = i;
            vals[i] = _vals[i];
        }

        for (int log = 1 ; (1 << log) <= n ; ++log)
        {
            for (int i = 1 ; i + (1 << log) - 1 <= n ; ++i)
            {
                sparse[log][i] = cmp(sparse[log - 1][i], sparse[log - 1][i + (1 << log - 1)]);
            }
        }
    
        for (int i = 1 ; i <= n ; ++i)
        {
            lg[i] = lg[i - 1];
            if ((1 << lg[i] + 1) < i)
            {
                lg[i]++;
            }
        }
    }

    int findMAX(int l, int r)
    {
        int log = lg[r - l + 1];
        return vals[cmp(sparse[log][l], sparse[log][r - (1 << log) + 1])];
    }

    int findIDX(int l, int r)
    {
        int log = lg[r - l + 1];
        return cmp(sparse[log][l], sparse[log][r - (1 << log) + 1]);
    }
};

int a[MAXN];
int b[MAXN];
int c[MAXN];
int d[MAXN];
int h[MAXN];
Sparse sparse;
std::stack <int> st;
std::vector <int> v;
int isClimb = -1;

void init(int N, std::vector <int> H) 
{
    n = N;
    for (int i = 1 ; i <= n ; ++i)
    {
        h[i] = H[i - 1];
    }

    sparse.build(h);
    st.push(0);

    for (int i = 1 ; i <= n ; ++i)
    {
        while (h[st.top()] > h[i])
        {
            st.pop();
        }

        a[i] = st.top();
        st.push(i);
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        if ((i == 1 || h[i - 1] < h[i]) && (i == n || h[i] > h[i + 1]))
        {
            isClimb = i;
            break;
        }
    }

    for (int i = 1 ; i < isClimb ; ++i)
    {
        if (h[i] > h[i + 1])
        {
            isClimb = -1;
            break;
        }
    }

    if (isClimb != -1)
    {
        for (int i = isClimb ; i < n ; ++i)
        {
            if (h[i] < h[i + 1])
            {
                isClimb = -1;
                break;
            }
        }
    }

    while (!st.empty())
    {
        st.pop();
    }

    st.push(n + 1);
    for (int i = n ; i >= 1 ; --i)
    {
        while (h[st.top()] > h[i])
        {
            st.pop();
        }

        c[i] = st.top();
        st.push(i);
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        if (a[i] == i - 1)
        {
            b[i] = 0;
        } else
        {
            b[i] = sparse.findMAX(a[i] + 1, i - 1) - h[i];
        }

        if (c[i] == i + 1)
        {
            d[i] = 0;
        } else
        {
            d[i] = sparse.findMAX(i + 1, c[i] - 1) - h[i];
        }
    }

    for (int i = 1 ; i <= n ; ++i)
    {
        int curr = INF; 
        if (a[i] > 0) curr = std::min(curr, b[i]);
        if (c[i] < n + 1) curr = std::min(curr, d[i]);
        v.push_back(curr);
    }

    std::sort(v.begin(), v.end());
}

bool entered;
int vals[MAXN];
int prefix[MAXN];
int max_towers(int L, int R, int D) 
{
    L++; R++;
    if (isClimb != -1)
    {
        if (isClimb < L || R < isClimb)
        {
            return 1;
        }

        if (h[L] + D <= h[isClimb] && h[R] + D <= h[isClimb])
        {
            return 2;
        }

        return 1;
    }

    if (L == R)
    {
        return 1;
    }

    if (L == 1 && R == n)
    {
        int l = -1, r = n, mid;
        while (l < r - 1)
        {
            mid = (l + r) / 2;
            if (v[mid] < D) l = mid;
            else r = mid;
        }

        return n - r;
    }

    if (!entered)
    {
        entered = true;
        for (int i = 1 ; i <= n ; ++i)
        {
            if ((a[i] > 0 && b[i] < D) && (c[i] == n + 1 || d[i] >= D))
            {
                vals[i] = a[i];
            } else
            {
                vals[i] = INF;
            }
        }

        left.build(vals);
        for (int i = 1 ; i <= n ; ++i)
        {
            if ((c[i] <= n && d[i] < D) && (a[i] == 0 || b[i] >= D))
            {
                vals[i] = c[i];
            } else
            {
                vals[i] = 0;
            }
        }

        right.build(vals);
        for (int i = 1 ; i <= n ; ++i)
        {
            prefix[i] = prefix[i - 1];
            if ((a[i] == 0 || b[i] >= D) && (c[i] == n + 1 || d[i] >= D))
            {
                prefix[i]++;
            }
        }
    }

    int ans = 0;
    for (int i = L ; i <= R ; ++i)
    {
        if ((a[i] < L || b[i] >= D) && (c[i] > R || d[i] >= D))
        {
            ans++;
        }
    }

    int add = 0;
    int idx = sparse.findIDX(L, R);
    if (a[idx] < L && c[idx] > R) add++;
    if (a[idx] == 0 && a[idx] == n + 1) add++;
    return prefix[R] - prefix[L - 1] + left.query(L, R, L) + (R - L + 1 - right.query(L, R, R + 1)) + add;
}

Compilation message (stderr)

towers.cpp: In member function 'void MST::build(int, int, int, int*)':
towers.cpp:33:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |             if (lPtr == tree[2*node].size())
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~
towers.cpp:39:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |             if (rPtr == tree[2*node + 1].size())
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
towers.cpp: In member function 'void Sparse::build(int*)':
towers.cpp:118:88: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
  118 |                 sparse[log][i] = cmp(sparse[log - 1][i], sparse[log - 1][i + (1 << log - 1)]);
      |                                                                                    ~~~~^~~
towers.cpp:125:29: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
  125 |             if ((1 << lg[i] + 1) < i)
      |                       ~~~~~~^~~

• Subtask 1: 4 / 4
• Subtask 2: 0 / 11
• Subtask 3: 0 / 12
• Subtask 4: 14 / 14
• Subtask 5: 17 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23