Submission #1040892

#	Time	Username	Problem	Language	Result	Execution time	Memory
1040892		c2zi6	Towns (IOI15_towns)	C++14	100 / 100	11 ms	1048 KiB

towns

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<typename T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#include "towns.h"

int maxind(VL& a) {
    int ret;
    ll mx = -1e18;
    rep(i, a.size()) if (a[i] > mx) {
        mx = a[i];
        ret = i;
    }
    return ret;
}

map<PII, int> distances;
int getdist(int u, int v) {
    if (u == v) return 0;
    if (u > v) swap(u, v);
    if (!distances.count({u, v})) distances[{u, v}] = getDistance(u, v);
    return distances[{u, v}];
}

int hubDistance(int N, int SUBTASK) {
    distances = map<PII, int>();
    int n = N;
    /*rep(u, n) rep(v, n) getdist(u, v);*/
    VL dist0, distd1, distl, distr, disth;
    dist0 = distd1 = distl = distr = disth = VL(n);
    rep(u, n) dist0[u] = getdist(0, u);
    int d1 = maxind(dist0);
    rep(u, n) distd1[u] = getdist(d1, u);
    int d2 = maxind(distd1);

    ll R = 1e18;
    rep(u, n) {
        disth[u] = (distd1[u] + dist0[u] - dist0[d1])/2;
        if (disth[u] == dist0[u]) disth[u] = -1;
        else {
            distl[u] = distd1[u]-disth[u];
            distr[u] = distd1[d2] - distl[u];
            setmin(R, max(distl[u], distr[u]));
        }
    }
    VI anc(n);
    /* 0, on the left
     * 1, first hub
     * 2, second hub
     * 3, on the right
     */
    rep(u, n) {
        if (disth[u] == -1) {
            anc[u] = 3;
        } else if (max(distl[u], distr[u]) == R) {
            if (distl[u] <= distr[u]) anc[u] = 1;
            else anc[u] = 2;
        } else {
            if (distl[u] <= distr[u]) anc[u] = 0;
            else anc[u] = 3;
        }
    }

    int cnt[4]{};
    for (int x : anc) cnt[x]++;

    auto check = [&](int u, int v) {
        return disth[u] + disth[v] != getdist(u, v);
    };
    VI a;
    replr(HUBIND, 1, 2) {
        a = VI();
        rep(i, n) if (anc[i] == HUBIND) a.pb(i);
        if (a.size() == 0) continue;
        if (HUBIND == 1) {
            if (cnt[0] > N/2) continue;
            if (cnt[2] + cnt[3] > N/2) continue;
        } else {
            if (cnt[0] + cnt[1] > N/2) continue;
            if (cnt[3] > N/2) continue;
        }

        stack<int> st;
        int c = 0;
        for (int i : a) {
            if (!st.size()) st.push(i);
            else {
                int m = st.top();
                if (check(i, m)) c++;
                else {
                    st.push(i);
                    if (c) {
                        c--;
                        st.push(m);
                    }
                }
            }
        }
        int m = st.top();
        int ans = c+1;
        st.pop();
        if (st.size()) st.pop();
        while (st.size()) {
            if (check(st.top(), m)) {
                ans++;
                st.pop();
                if (st.size()) st.pop();
                else c++;
            } else {
                st.pop();
                c--;
                if (c == -1) return +R;
            }
        }
        if (c == 0) return +R;
        if (ans <= n/2) return +R;
    }
	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:139:37: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
  139 |                 if (c == -1) return +R;
      |                                     ^~
towns.cpp:142:28: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
  142 |         if (c == 0) return +R;
      |                            ^~
towns.cpp:143:32: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
  143 |         if (ans <= n/2) return +R;
      |                                ^~
towns.cpp:145:9: warning: conversion from 'll' {aka 'long long int'} to 'int' may change value [-Wconversion]
  145 |  return -R;
      |         ^~
towns.cpp:52:28: warning: unused parameter 'SUBTASK' [-Wunused-parameter]
   52 | int hubDistance(int N, int SUBTASK) {
      |                        ~~~~^~~~~~~
towns.cpp: In function 'int maxind(VL&)':
towns.cpp:41:12: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
   41 |     return ret;
      |            ^~~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:65:52: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
   65 |         disth[u] = (distd1[u] + dist0[u] - dist0[d1])/2;
      |                                                    ^
towns.cpp:69:33: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
   69 |             distr[u] = distd1[d2] - distl[u];
      |                                 ^

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 39 / 39