Submission #943521

#	Time	Username	Problem	Language	Result	Execution time	Memory
943521		Zero_OP	Cat in a tree (BOI17_catinatree)	C++14	100 / 100	180 ms	54216 KiB

catinatree

#include<bits/stdc++.h>

using namespace std;
using int64 = int64_t;

#define     REP(i, n) for(int i = 0, _n = n; i < _n; ++i)
#define    REPD(i, n) for(int i = n - 1; i >= 0; --i)
#define  FOR(i, l, r) for(int i = l, _r = r; i <= _r; ++i)
#define FORD(i, r, l) for(int i = r, _l = l; i >= _l; --i)
#define          left __left
#define         right __right
#define          prev __prev
#define          next __next
#define           div __div
#define            pb push_back
#define            pf push_front
#define         sz(v) (int)v.size()
#define      range(v) begin(v), end(v)
#define    compact(v) v.erase(unique(range(v)), end(v))
#define      debug(v) "[" #v " = " << (v) << "]"

template<typename T>
    bool minimize(T& a, const T& b){
        if(a > b){
            a = b;
            return true;
        }
        return false;
    }

template<typename T>
    bool maximize(T& a, const T& b){
        if(a < b){
            a = b;
            return true;
        }
        return false;
    }

template<int dimension, class T>
struct vec : public vector<vec<dimension - 1, T>> {
    static_assert(dimension > 0, "Dimension must be positive !\n");
    template<typename... Args>
    vec(int n = 0, Args... args) : vector<vec<dimension - 1, T>>(n, vec<dimension - 1, T>(args...)) {}
};

template<class T>
struct vec<1, T> : public vector<T> {
    vec(int n = 0, T val = T()) : vector<T>(n, val) {}
};

void init(void);
void process(void);

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

    #define task "antuvu"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    int T = 1; //cin >> T;
    while(T--) {
        init();
        process();
    }

    return 0;
}

const int MAX = 2e5 + 5;

int n, d, timer_dfs, depth[MAX], spt[20][MAX * 2], pos[MAX], par[MAX], count_children[MAX], dp[MAX];
vector<int> adj[MAX];
bool del[MAX];

void init(){
    cin >> n >> d;
    FOR(i, 1, n - 1){
        int p; cin >> p;
        adj[p].pb(i);
        adj[i].pb(p);
    }
}

void pre_dfs(int u, int pre){
    spt[0][pos[u] = timer_dfs++] = u;
    for(int v : adj[u]) if(v != pre){
        depth[v] = depth[u] + 1;
        pre_dfs(v, u);
        spt[0][timer_dfs++] = u;
    }
}

int f(int a, int b){
    return depth[a] < depth[b] ? a : b;
}

void prepareRMQ(){
    for(int i = 1; (1 << i) <= timer_dfs; ++i){
        for(int j = 0; j + (1 << i) <= timer_dfs; ++j){
            spt[i][j] = f(spt[i - 1][j], spt[i - 1][j + (1 << (i - 1))]);
        }
    }
}

int getLCA(int u, int v){
    u = pos[u], v = pos[v];
    if(u > v) swap(u, v);
    int step = __lg(v - u + 1);
    return f(spt[step][u], spt[step][v - (1 << step) + 1]);
}

int get_distance(int u, int v){
    return depth[u] + depth[v] - 2 * depth[getLCA(u, v)];
}

int dfs_size(int u, int pre){
    count_children[u] = 1;
    for(int v : adj[u]) if(v != pre and !del[v]){
        count_children[u] += dfs_size(v, u);
    }
    return count_children[u];
}

int find_centroid(int u, int pre, int target){
    for(int v : adj[u]) if(v != pre and !del[v] and count_children[v] * 2 > target){
        return find_centroid(v, u, target);
    }
    return u;
}

void decompose(int u, int e){
    int c = find_centroid(u, e, dfs_size(u, e));
    del[c] = true; par[c] = e;

    for(int v : adj[c]) if(!del[v]) decompose(v, c);
}

void update(int u){
    int v = u;
    while(v != -1){
        minimize(dp[v], get_distance(v, u));
        v = par[v];
    }
}

int query(int u){
    int ans = INT_MAX, v = u;
    while(v != -1){
        minimize(ans, dp[v] + get_distance(u, v));
        v = par[v];
    }
    return ans;
}

void process(){
    pre_dfs(0, -1);
    prepareRMQ();
    decompose(0, -1);

    memset(dp, 0x3f, sizeof(dp));
    vector<pair<int, int>> nodes;
    REP(i, n){
        nodes.pb(make_pair(depth[i], i));
    }

    int ans = 0;
    sort(range(nodes), greater<pair<int, int>>());
    for(auto [x, u] : nodes){
        if(query(u) >= d){
            ++ans;
            update(u);
        }
    }
    cout << ans << '\n';
}

Compilation message (stderr)

catinatree.cpp: In function 'void process()':
catinatree.cpp:172:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  172 |     for(auto [x, u] : nodes){
      |              ^
catinatree.cpp: In function 'int main()':
catinatree.cpp:60:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
catinatree.cpp:61:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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