Submission #992367

#	Time	Username	Problem	Language	Result	Execution time	Memory
992367		cpptowin	Hard route (IZhO17_road)	C++17	100 / 100	418 ms	143956 KiB

road

#include <bits/stdc++.h>
#define fo(i, d, c) for (int i = d; i <= c; i++)
#define fod(i, c, d) for (int i = c; i >= d; i--)
#define maxn 1000010
#define N 1010
#define fi first
#define se second
#define pb emplace_back
#define en cout << "\n";
#define int long long
#define inf (int)1e18
#define pii pair<int, int>
#define vii vector<pii>
#define lb(x) x & -x
#define bit(i, j) ((i >> j) & 1)
#define offbit(i, j) (i ^ (1LL << j))
#define onbit(i, j) (i | (1LL << j))
#define vi vector<int>
template <typename T1, typename T2>
bool minimize(T1 &a, T2 b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
bool maximize(T1 &a, T2 b)
{
    if (a < b)
    {
        a = b;
        return true;
    }
    return false;
}
using namespace std;
const int nsqrt = 450;
const int mod = 1e9 + 7;
int n, maxx[maxn], cnt[maxn];
vi ke[maxn];
pii ans = {0,1};
void dfs(int u, int par = 0)
{
    maxx[u] = 0;
    cnt[u] = 1;
    for (int v : ke[u])
        if (v != par)
        {
            dfs(v, u);
            if (maxx[u] < maxx[v] + 1)
            {
                maxx[u] = maxx[v] + 1;
                cnt[u] = cnt[v];
            }
            else if (maxx[u] == maxx[v] + 1)
                cnt[u] += cnt[v];
        }
}
void dfs2(int u, pii par_dist, int par)
{
    vii path;
    if (u > 1 or ke[u].size() == 1)
        path.pb(par_dist);
    for (int v : ke[u])
        if (v != par)
            path.pb(maxx[v] + 1, cnt[v]);
    sort(path.begin(), path.end(), greater<pii>());
    // cout << u << ' ' << path.size();en;
    if (path.size() > 2)
    {
        int a = path[0].fi;
        int b = path[1].fi;
        int c = path[2].fi;
        int fre = 0;
        int tot = 0;
        int longest_route = a * (b + c);
        // a >= b >= c => a * (b + c) >= b * (c + a) , a * (b + c) >= c * (a + b)
        for (auto [len, dem] : path)
            if (len == c)
                tot += dem;
        if (a != b and b != c)
            fre = tot * path[1].se;
        else if (a == b and b == c)
        {
            // tot = (x + y + z + ...)
            fre = tot * tot; // = (x + y + z + ...) ^ 2
            for (auto [len, dem] : path)
                if (len == a)
                    fre -= dem * dem;
            fre /= 2; // = xy + yz + zx + ...
        }
        else if (a == b and b != c)
            fre = (path[0].se + path[1].se) * tot;
        else if (a != b and b == c)
        {
            fre = tot * tot;
            for (auto [len, dem] : path)
                if (len == c)
                    fre -= dem * dem;
            fre /= 2;
        }
        // cout << longest_route << "\n";
        if (ans.fi < longest_route)
            ans = {longest_route, fre};
        else if (ans.fi == longest_route)
            ans.se += fre;
    }
    // cout << u << ' ' << ans.fi << ' ' << ans.se << "\n";
    pii longest1 = {0, 0};
    pii longest2 = {0, 0};
    for(auto [len,dem] : path)
    {
        if (len + 1 > longest1.fi)
        {
            swap(longest1, longest2);
            longest1 = {len + 1, dem};
        }
        else if(len + 1 == longest1.fi) longest1.se += dem;
        else if(len + 1 > longest2.fi) longest2 = {len + 1,dem};
        else if(len + 1 == longest2.fi) longest2.se += dem;
    }
    for (int v : ke[u])
        if (v != par)
        {
            if (maxx[v] + 2 == longest1.fi)
            {
                if (cnt[v] == longest1.se)
                    dfs2(v, longest2, u);
                else
                    dfs2(v, {longest1.fi, longest1.se - cnt[v]}, u);
            }
            else
                dfs2(v, longest1, u);
        }
}
main()
{
#define name "TASK"
    if (fopen(name ".inp", "r"))
    {
        freopen(name ".inp", "r", stdin);
        freopen(name ".out", "w", stdout);
    }
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n;
    fo(i, 1, n - 1)
    {
        int u, v;
        cin >> u >> v;
        ke[u].pb(v);
        ke[v].pb(u);
    }
    dfs(1);
    dfs2(1, {0, 1}, 1);
    cout << ans.fi << ' ' << ans.se;
}

Compilation message (stderr)

road.cpp:139:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  139 | main()
      | ^~~~
road.cpp: In function 'int main()':
road.cpp:144:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  144 |         freopen(name ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
road.cpp:145:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  145 |         freopen(name ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 19 / 19
• Subtask 2: 33 / 33
• Subtask 3: 48 / 48