Submission #428415

#	Time	Username	Problem	Language	Result	Execution time	Memory
428415		Popax21	Finding Routers (IOI20_routers)	C++14	100 / 100	3 ms	972 KiB

routers

#include <stdio.h>
#include <assert.h>
#include <map>
#include "routers.h"

std::vector<int> cache;
std::multimap<int, int> qs;

int query(int p) {
    if(cache[p] >= 0) return cache[p];
    int r = use_detector(p);
    cache[p] = r;
    qs.emplace(r, p);
    return r;
}

int bsearch(int l, int r, int n) {
    assert(l < r);

    if(l == r-1) return l;
    int m = l + (r - l) / 2;

    int mr = query(m);

    if(mr != n) return bsearch(l, m, n);
    else return bsearch(m, r, n);
}

std::vector<int> find_routers(int l, int n, int q) {
    cache.resize(l+1);
    std::fill(cache.begin(), cache.end(), -1);

    std::vector<int> rs(n);
    rs[0] = 0;

    int pr = 0;
    for(int c = 1; c < n; c++) {
        int lp = rs[pr]+1, rp = l+1;

        auto li = qs.lower_bound(pr), ri = qs.upper_bound(pr);
        if(li != qs.end() && lp < li->second) lp = li->second;
        if(ri != qs.end() && ri->second < rp) rp = ri->second;
        // printf("pr %d l %d r %d %d %d\n", pr, lp, rp, ri->first, ri->second);

        int p = bsearch(lp, rp, pr)+1;
        int r = query(p);

        rs[r] = 2*p - rs[pr];
        if(r > pr) rs[r] -= 2;

        // printf("pr %d r %d p %d pp %d p' %d\n", pr, r, p, rs[pr], rs[r]);
        pr = r;
    }

    return rs;
}

• Subtask 1: 16 / 16
• Subtask 2: 21 / 21
• Subtask 3: 23 / 23
• Subtask 4: 40 / 40