Submission #1061838

#	Time	Username	Problem	Language	Result	Execution time	Memory
1061838		RecursiveCo	Sky Walking (IOI19_walk)	C++17	43 / 100	237 ms	22736 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()
    if (max(n, m) <= 50) {
        // s and g can be anything, but n and m are small anyway so it doesn't matter.
        map<pair<int, int>, vector<array<int, 3>>> adjList;
        vector<vector<int>> pts(n);
        for (int i = 0; i < m; i++) {
            vector<int> enough;
            for (int j = l[i]; j <= r[i]; j++) {
                if (h[j] >= y[i]) {
                    pts[j].push_back(y[i]);
                    enough.push_back(j);
                }
            }
            int t = enough.size();
            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]});
            }
        }
        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: 0 / 14
• Subtask 3: 15 / 15
• Subtask 4: 18 / 18
• Subtask 5: 0 / 43