Submission #1356432

#TimeUsernameProblemLanguageResultExecution timeMemory
1356432Desh03Rainforest Jumps (APIO21_jumps)C++20
48 / 100
300 ms49968 KiB
#include <bits/stdc++.h>

using namespace std;

mt19937 rng(chrono::steady_clock().now().time_since_epoch().count());

struct SegmentTree {
    vector<pair<int, int>> st;
    int n;
    SegmentTree() { }
    void init(const vector<int> &v) {
        n = v.size();
        while (n & n - 1) ++n;
        st.resize(n << 1, {0, 0});
        for (int i = 0; i < v.size(); i++) {
            st[i + n] = {v[i], i};
        }
        for (int i = n - 1; i > 0; i--) {
            st[i] = max(st[i << 1], st[i << 1 | 1]);
        }
    }
    int find_last(int v, int l, int r, int ql, int qr, int x) {
        if (l > qr || r < ql || st[v].first < x) return -1;
        if (l >= ql && r <= qr) {
            while (l < r) {
                int m = l + r >> 1;
                if (st[v << 1 | 1].first >= x) v = v << 1 | 1, l = m + 1;
                else v <<= 1, r = m;
            }
            return l;
        }
        int m = l + r >> 1;
        int k = find_last(v << 1 | 1, m + 1, r, ql, qr, x);
        if (k != -1) return k;
        return find_last(v << 1, l, m, ql, qr, x);
    }
    int qry(int l, int r) {
        pair<int, int> mx = {0, 0};
        for (l += n, r += n + 1; l < r; l >>= 1, r >>= 1) {
            if (l & 1) mx = max(mx, st[l++]);
            if (r & 1) mx = max(mx, st[--r]);
        }
        return mx.second;
    }
    int find_last(int l, int r, int x) {
        return find_last(1, 0, n - 1, l, r, x);
    }
} sgt;

const int N = 2e5, lg = 18, inf = 1e9;
int n, nxt[lg][N], prv[lg][N], g[lg][N], h[N];

void init(int N, vector<int> H) {
    n = N;
    for (int i = 0; i < n; i++) {
        h[i] = H[i];
    }
    sgt.init(H);
    stack<int> st;
    for (int i = 0; i < n; i++) {
        while (st.size() && h[st.top()] <= h[i]) st.pop();
        prv[0][i] = st.size() ? st.top() : -1;
        st.push(i);
    }
    while (st.size()) st.pop();
    for (int i = n - 1; i >= 0; i--) {
        while (st.size() && h[st.top()] <= h[i]) st.pop();
        nxt[0][i] = st.size() ? st.top() : -1;
        st.push(i);
    }
    for (int i = 0; i < n; i++) {
        if (nxt[0][i] == -1) g[0][i] = prv[0][i];
        else if (prv[0][i] == -1) g[0][i] = nxt[0][i];
        else g[0][i] = (h[nxt[0][i]] >= h[prv[0][i]] ? nxt[0][i] : prv[0][i]);
    }
    for (int i = 1; i < lg; i++) {
        for (int j = 0; j < n; j++) {
            prv[i][j] = prv[i - 1][j] == -1 ? -1 : prv[i - 1][prv[i - 1][j]];
            nxt[i][j] = nxt[i - 1][j] == -1 ? -1 : nxt[i - 1][nxt[i - 1][j]];
            g[i][j] = g[i - 1][j] == -1 ? -1 : g[i - 1][g[i - 1][j]];
        }
    }
}

int minimum_jumps(int a, int b, int c, int d) {
    int k = sgt.find_last(a, b, h[c]);
    if (k == b) return -1;
    b = sgt.qry((k == -1 ? a : k + 1), b);
    int ans = 0;
    for (int i = lg - 1; i >= 0; i--) {
        if (g[i][b] != -1 && h[g[i][b]] < h[c]) {
            b = g[i][b];
            ans += (1 << i);
        }
    }
    if (b > c) return -1;
    for (int i = lg - 1; i >= 0; i--) {
        if (nxt[i][b] != -1 && h[nxt[i][b]] <= h[c]) {
            b = nxt[i][b];
            ans += (1 << i);
        }
    }
    return b == c ? ans : -1;
}
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