Submission #1061871

#	Time	Username	Problem	Language	Result	Execution time	Memory
1061871		RecursiveCo	Sky Walking (IOI19_walk)	C++17	57 / 100	3450 ms	320060 KiB

walk

#include <bits/stdc++.h>
#include "walk.h"

using namespace std;

long long min_distance(vector<int> x, vector<int> h, vector<int> l, vector<int> r, vector<int> y, int s, int g) {
    int n = x.size(); // = h.size()
    int m = l.size(); // = r.size() = y.size()
    
        // s and g can be anything, but n and m are small anyway so it doesn't matter.
        // or I suppose also with small numbers of intersections.
        vector<pair<int, int>> sorted;
        for (int i = 0; i < m; i++) {
            sorted.push_back({y[i], i});
        }
        sort(sorted.rbegin(), sorted.rend());
        int maxi = -1;
        map<pair<int, int>, vector<array<int, 3>>> adjList;
        vector<vector<int>> pts(n);
        set<int> tall;
        int ptr1 = 0;
        vector<pair<int, int>> buildings;
        for (int i = 0; i < n; i++) {
            buildings.push_back({h[i], i});
        }
        sort(buildings.rbegin(), buildings.rend());
        for (int k = 0; k < m; k++) {
            int yc = sorted[k].first;
            int i = sorted[k].second;
            while (ptr1 < n && buildings[ptr1].first >= yc) {
                tall.insert(buildings[ptr1].second);
                ptr1++;
            }
            vector<int> enough;
            for (auto it = tall.lower_bound(l[i]); it != tall.end(); it++) {
                if ((*it) > r[i]) break;
                enough.push_back(*it);
                pts[*it].push_back(y[i]);
            }
            int t = enough.size();
            maxi = max(maxi, t);
            if (maxi > 50) break;
            for (int j = 0; j < t - 1; j++) {
                int x1 = enough[j];
                int x2 = enough[j + 1];
                adjList[{x1, y[i]}].push_back({x2, y[i], x[x2] - x[x1]});
                adjList[{x2, y[i]}].push_back({x1, y[i], x[x2] - x[x1]});
            }
        }
        if (maxi <= 50) {
            for (int i = 0; i < n; i++) {
                pts[i].push_back(0);
                sort(pts[i].begin(), pts[i].end());
                int t = pts[i].size();
                for (int j = 0; j < t - 1; j++) {
                    int y1 = pts[i][j];
                    int y2 = pts[i][j + 1];
                    adjList[{i, y1}].push_back({i, y2, y2 - y1});
                    adjList[{i, y2}].push_back({i, y1, y2 - y1});
                }
            }
            priority_queue<pair<long long, pair<int, int>>, vector<pair<long long, pair<int, int>>>, greater<pair<long long, pair<int, int>>>> pq;
            map<pair<int, int>, long long> dist;
            set<pair<int, int>> visited;
            pq.push({0ll, {s, 0}});
            while (!pq.empty()) {
                auto top = pq.top();
                pq.pop();
                if (visited.find(top.second) != visited.end()) continue;
                visited.insert(top.second);
                dist[top.second] = top.first;
                for (auto con: adjList[top.second]) {
                    if (visited.find({con[0], con[1]}) == visited.end()) {
                        pq.push({top.first + con[2], {con[0], con[1]}});
                    }
                }
            }
            return dist.find({g, 0}) == dist.end()? -1: dist[{g, 0}];
        }
    
    // Assume s = 0, g = n - 1 and h consists of equal elements.
    long long ans = x[n - 1] - x[0];
    map<pair<int, int>, long long> dp;
    vector<array<int, 4>> events;
    for (int i = 0; i < m; i++) {
        events.push_back({r[i] - 1, y[i], i, 1});
        events.push_back({l[i] - 1, y[i], i, 0});
    }
    sort(events.rbegin(), events.rend());
    vector<vector<int>> right(n);
    for (int i = 0; i < m; i++) right[r[i]].push_back(i);
    set<pair<int, int>> open;
    int ptr = 0;
    for (int i = n - 1; i >= 0; i--) {
        while (ptr < 2 * m && events[ptr][0] >= i) {
            int yc = events[ptr][1];
            int ind = events[ptr][2];
            int typ = events[ptr][3];
            if (typ) {
                open.insert({yc, ind});
            } else {
                open.erase({yc, ind});
            }
            ptr++;
        }
        for (int ind: right[i]) {
            long long val = 1e18;
            auto it = open.lower_bound({y[ind], -1});
            if (it != open.end()) {
                val = min(val, (long long) ((*it).first - y[ind]) + dp[{r[(*it).second], (*it).first}]);
            }
            if (it != open.begin()) {
                it--;
                val = min(val, (long long) (y[ind] - (*it).first) + dp[{r[(*it).second], (*it).first}]);
            }
            dp[{i, y[ind]}] = i == n - 1? y[ind]: val;
        }
    }
    long long extra = 1e18;
    for (int i = 0; i < m; i++) {
        if (l[i] == 0) {
            extra = min(extra, y[i] + dp[{r[i], y[i]}]);
        }
    }
    ans += extra;
    if (ans >= 1e18) return -1;
    return ans;
}

• Subtask 1: 10 / 10
• Subtask 2: 14 / 14
• Subtask 3: 15 / 15
• Subtask 4: 18 / 18
• Subtask 5: 0 / 43