Submission #1093897

#	Time	Username	Problem	Language	Result	Execution time	Memory
1093897		Cadoc	Cat in a tree (BOI17_catinatree)	C++14	100 / 100	249 ms	102080 KiB

catinatree

/*
    Author: Cadocx
    Codeforces: https://codeforces.com/profile/Kadoc
    VNOJ: oj.vnoi.info/user/Cadoc
*/

#include <bits/stdc++.h>
using namespace std;

// input/output
#define fastIO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define el cout << '\n'
#define debug(x) cout << #x << " = " << x << '\n'
#define execute cerr << "Time elapsed: " << (1.0 * clock() / CLOCKS_PER_SEC) << "s"
// #pragma GCC optimize("O2", "unroll-loops", "Ofast")
// #pragma GCC target("avx,avx2,fma")
//data type
#define ll long long
#define ull unsigned long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define piv pair<int, vector<int>>
#define vi vector<int>
#define vl vector<ll>
#define vc vector<char>
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return 1; }; return 0; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return 1; }; return 0; }
//STL
#define sz(x) (int)(x).size()
#define FOR(i,l,r) for(auto i = l; i <= r; i++)
#define FORD(i,r,l) for(auto i = r; i >= l; i--)
#define forin(i,a) for(auto i : a)
#define pb push_back
#define eb emplace_back
#define pf push_front
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
//bitmask
#define bitcnt(n) __builtin_popcount(n)
#define mask(i) (1 << (i))
#define bit(n, i) (((n) >> (i)) & 1)
#define set_on(n, i) ((n) | mask(i))
#define set_off(n, i) ((n) & ~mask(i))
//constant
#define N 1000005
#define MOD 1000230007
#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define base 31
#define Kadoc 0
#define Min(u, v) h[u] < h[v]? u:v

int n, d;
int h[N], Node[N], pos[N], Timer = 0;
int rmq[N][33];
int sz[N], del[N], par[N];
int ans[N];
vector<int> g[N];

void dfs(int u, int p = -1){
    Node[++Timer] = u;
    pos[u] = Timer;

    for(int v:g[u]) if(v != p){
        h[v] = h[u] + 1;
        dfs(v, u);
        Node[++Timer] = u;
    }
}

void dfs_sz(int u, int p = -1){
    sz[u] = 1;
    for(int v:g[u]) if(v != p && !del[v]){
        dfs_sz(v, u);
        sz[u] += sz[v];
    }
}

int findcentroid(int u, int p, int n){
    for(int v:g[u]) if(v != p && !del[v] && sz[v] > n/2) return findcentroid(v, u, n);
    return u;
}

void centroidDecomp(int u, int p = -1){
    dfs_sz(u);
    u = findcentroid(u, p, sz[u]);

    del[u] = 1;
    par[u] = p;

    for(int v:g[u]) if(v != p && !del[v]) centroidDecomp(v, u);
}

int lca(int u, int v){
    int l = pos[u], r = pos[v];
    if(l > r) swap(l, r);

    int k = 31 - __builtin_clz(r-l+1);
    return Min(rmq[l][k], rmq[r-mask(k)+1][k]);
}

int dist(int u, int v){
    return h[u] + h[v] - 2*h[lca(u, v)];
}

void upd(int u){
    for(int v = u; v > 0; v = par[v]) minimize(ans[v], dist(u, v));
}

int get(int u){
    int Ans = INF;
    for(int v = u; v > 0; v = par[v]) minimize(Ans, ans[v] + dist(u, v));
    return Ans;
}

void solve(){
    cin >> n >> d;
    FOR(i, 2, n){
        int x; cin >> x; x++;
        g[i].pb(x);
        g[x].pb(i);
    }

    dfs(1);
    centroidDecomp(1);

    FOR(i, 1, Timer) rmq[i][0] = Node[i];
    for(int j=1; mask(j)<=Timer; ++j){
        for(int i=1; i+mask(j)-1<=Timer; ++i){
            rmq[i][j] = Min(rmq[i][j-1], rmq[i+mask(j-1)][j-1]);
        }
    }

    vector<pii> v;
    FOR(i, 1, n) v.pb({-h[i], i});
    sort(all(v));

    memset(ans, 0x3f, sizeof ans);
    int Ans = 0;
    for(auto [depth, u]:v){
        if(get(u) >= d){
            Ans++;
            upd(u);
        }
    }

    cout << Ans;
}

int main(){
    #define NAME "TASK"
    if(fopen(NAME".inp", "r")){
        freopen(NAME".inp", "r", stdin);
        freopen(NAME".out", "w", stdout);
    }

    fastIO;
    
    if(Kadoc){
        int tc; cin >> tc;
        while(tc--){
            solve();
        }
    } else solve();
}

Compilation message (stderr)

catinatree.cpp: In function 'void solve()':
catinatree.cpp:141:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  141 |     for(auto [depth, u]:v){
      |              ^
catinatree.cpp: In function 'int main()':
catinatree.cpp:154:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  154 |         freopen(NAME".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
catinatree.cpp:155:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  155 |         freopen(NAME".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49