Submission #1133380

#	Time	Username	Problem	Language	Result	Execution time	Memory
1133380		steveonalex	Torrent (COI16_torrent)	C++20	100 / 100	69 ms	23624 KiB

torrent

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
    double cur = rngesus(0, MASK(60) - 1);
    cur /= MASK(60) - 1;
    return l + cur * (r - l);
}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }
const int N = 3e5 + 69;
int n, u, v; 
vector<int> graph[N];

int go(int u, int p){
    vector<int> child;
    for(int v: graph[u]) if (v != p){
        int cur = go(v, u);
        child.push_back(cur);
    }
    sort(ALL(child));
    int ma = 0;
    int cnt = 0;
    while(child.size()){
        maximize(ma, child.back() + ++cnt);
        child.pop_back();
    }
    return ma;
}

int parent[N];

void dfs(int u, int p){
    parent[u] = p;
    for(int v: graph[u]) if (v != p)
        dfs(v, u);
}

vector<int> get_chain(int u, int v){
    vector<int> ans;
    dfs(u, 0);
    while(v != u){
        ans.push_back(v);
        v = parent[v];
    }
    ans.push_back(u);
    reverse(ALL(ans));
    return ans;
}

int solve(){
    cin >> n >> u >> v;
    for(int i = 1; i< n; ++i){
        int u, v; cin >> u >> v;
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    if (u == v)
        return go(u, 0);
    vector<int> chain = get_chain(u, v);
    vector<bool> on_chain(n+1);
    for(int i: chain) on_chain[i] = true;

    int m = chain.size();
    vector<vector<int>> jack(m);
    for(int i = 0; i < m; ++i){
        int u = chain[i];
        for(int v: graph[u]) if (!on_chain[v]){
            int cur = go(v, u);
            jack[i].push_back(cur);
        }
        sort(ALL(jack[i]), greater<int>());
    }

    int l = 0, r = n;
    while(l < r){
        int mid = (l + r) >> 1;

        int t = 0;
        int L = -1, R = m;
        for(int i = 0; i < m; ++i){
            int e = 0, ma_e = 0;
            bool continue_further = true;
            for(int j: jack[i]){
                e++;
                if (j + e + t > mid) {
                    continue_further = false;
                    break;
                }
                else if (j + e + t == mid){
                    ma_e = e;
                }
            }
            if (continue_further == false) break;
            t += ma_e + 1;
            L = i;
        }
        t = 0;
        for(int i = m - 1; i >= 0; --i){
            int e = 0, ma_e = 0;
            bool continue_further = true;
            for(int j: jack[i]){
                e++;
                if (j + e + t > mid) {
                    continue_further = false;
                    break;
                }
                else if (j + e + t == mid){
                    ma_e = e;
                }
            }
            if (continue_further == false) break;
            t += ma_e + 1;
            R = i;
        }

        if (L + 1 >= R) r = mid;
        else l = mid + 1;
    }
    return l;
}

int main(void){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
 
    clock_t start = clock();
 
    cout << solve() << "\n";    
 
    cerr << "Time elapsed: " << clock() - start << "ms!\n";
 
    return 0;
}

• Subtask 1: 31 / 31
• Subtask 2: 69 / 69