Submission #362255

#	Time	Username	Problem	Language	Result	Execution time	Memory
362255		alextodoran	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	304 ms	171756 KiB

catinatree

/**
 ____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|

**/

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N_MAX = 200002;

const int BUFFER_SIZE = 100000;

char buffer[BUFFER_SIZE];
int bpos = BUFFER_SIZE - 1;

char read_char ()
{
    bpos++;
    if(bpos == BUFFER_SIZE)
    {
        fread(buffer, sizeof(char), BUFFER_SIZE, stdin);
        bpos = 0;
    }
    return buffer[bpos];
}

bool isDigit[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

int read_int ()
{
    char c;
    while(!isDigit[c = read_char()]);
    int ans = 0;
    while(isDigit[c])
    {
        ans = ans * 10 + c - '0';
        c = read_char();
    }
    return ans;
}

int n, maxd;

int parent[N_MAX];

vector <int> sons[N_MAX];

int depth[N_MAX];

deque <int> dp[N_MAX];

int vsum[N_MAX];
int vmax[N_MAX];

void solve (int u)
{
    if(sons[u].empty() == true)
    {
        dp[u].push_back(1);
        return;
    }
    for(int v : sons[u])
    {
        solve(v);
        depth[u] = max(depth[u], depth[v] + 1);
    }
    int secondDepth = -1;
    bool firstDepth = false;
    for(int v : sons[u])
        if(depth[v] + 1 == depth[u] && firstDepth == false)
            firstDepth = true;
        else
            secondDepth = max(secondDepth, depth[v]);
    for(int d = 0; d <= min(maxd / 2, secondDepth + 1); d++)
        vsum[d] = vmax[d] = 0;
    for(int v : sons[u])
    {
        int lim = min({maxd / 2, depth[v] + 1, secondDepth + 1});
        for(int d = 1; d <= lim; d++)
        {
            int val = 0;
            if(maxd - d - 1 <= depth[v])
                val = dp[v][maxd - d - 1];
            vsum[d] += val;
            vmax[d] = max(vmax[d], dp[v][d - 1] - val);
        }
    }
    int deepSon = -1;
    for(int v : sons[u])
        if(deepSon == -1 || depth[v] > depth[deepSon])
            deepSon = v;
    int sum = 1;
    for(int v : sons[u])
        if(maxd - 1 <= depth[v])
            sum += dp[v][maxd - 1];
    swap(dp[u], dp[deepSon]);
    dp[u].push_front(sum);
    for(int v : sons[u])
        if(v != deepSon)
        {
            int lim = min(maxd - 1, depth[v] + 1);
            for(int d = (maxd + 1) / 2; d <= lim; d++)
                dp[u][d] += dp[v][d - 1];
        }
    for(int d = 1; d <= min(maxd / 2, secondDepth + 1); d++)
        dp[u][d] = vsum[d] + vmax[d];
    for(int d = min(maxd - 2, secondDepth + 1); d >= 0; d--)
        dp[u][d] = max(dp[u][d], dp[u][d + 1]);
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    n = read_int();
    maxd = read_int();
    for(int i = 2; i <= n; i++)
        parent[i] = read_int() + 1;
    for(int i = 2; i <= n; i++)
        sons[parent[i]].push_back(i);
    solve(1);
    cout << dp[1][0] << "\n";
    return 0;
}

Compilation message (stderr)

catinatree.cpp: In function 'int read_int()':
catinatree.cpp:54:22: warning: array subscript has type 'char' [-Wchar-subscripts]
   54 |     while(!isDigit[c = read_char()]);
      |                    ~~^~~~~~~~~~~~~
catinatree.cpp:56:19: warning: array subscript has type 'char' [-Wchar-subscripts]
   56 |     while(isDigit[c])
      |                   ^
catinatree.cpp: In function 'char read_char()':
catinatree.cpp:27:14: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   27 |         fread(buffer, sizeof(char), BUFFER_SIZE, stdin);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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