Submission #313819

#	Time	Username	Problem	Language	Result	Execution time	Memory
313819		BeanZ	Untitled (POI11_dyn)	C++14	100 / 100	1997 ms	36984 KiB

Main

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

#define ll int
#define endl '\n'
const int N = 3e5 + 5;
ll cnt = 0, mid;
ll dp[N], hp[N], a[N], farcry[N];
vector<ll> node[N];
void dfs(ll u, ll p){
    hp[u] = 0;
    for (auto j : node[u]){
        if (j == p) continue;
        dfs(j, u);
        farcry[u] = min(farcry[u], farcry[j] + 1);
    }
    if (a[u] == 1 && farcry[u] > mid) hp[u] = 1, dp[u] = 0;
    for (auto j : node[u]){
        if (j == p) continue;
        if (hp[j]){
            if ((farcry[u] + dp[j] + 1) <= mid) continue;
            else dp[u] = max(dp[u], dp[j] + 1), hp[u] = 1;
        }
    }
    if (dp[u] == mid){
        cnt++;
        dp[u] = -1e9;
        farcry[u] = 0;
        hp[u] = 0;
    }
    if (u == 1){
        if (dp[u] == 0 && a[u] && farcry[u] > mid) cnt++;
        else if (dp[u] >= 1) cnt++;
    }
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    if (fopen("A.inp", "r")){
        freopen("test.inp", "r", stdin);
        freopen("test.out", "w", stdout);
    }
    ll n, m;
    cin >> n >> m;
    ll res = 0;
    for (int i = 1; i <= n; i++){
        cin >> a[i];
        if (a[i] == 1) res++;
    }
    for (int i = 1; i < n; i++){
        ll u, v;
        cin >> u >> v;
        node[u].push_back(v);
        node[v].push_back(u);
    }
    if (res <= m) return cout << 0, 0;
    ll l = 1, h = n;
    while (l <= h){
        mid = (l + h) >> 1;
        cnt = 0;
        memset(hp, 0, sizeof(hp));
        for (int i = 1; i <= n; i++) farcry[i] = 1e9, dp[i] = -1e9;
        dfs(1, 1);
        if (cnt > m) l = mid + 1;
        else h = mid - 1;
    }
    cout << l;
}
/*
*/

Compilation message (stderr)

dyn.cpp: In function 'int main()':
dyn.cpp:41:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   41 |         freopen("test.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
dyn.cpp:42:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   42 |         freopen("test.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10