Submission #419003

#	Time	Username	Problem	Language	Result	Execution time	Memory
419003		egekabas	Mousetrap (CEOI17_mousetrap)	C++14	20 / 100	1751 ms	74328 KiB

mousetrap

#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<int, int> pii;
typedef pair<ld, ld> pld;
int n, t, m;
vector<int> g[1000009];
int trap[1000009];
int dp[1000009];
int edgecnt[1000009];

void dfs(int v, int prt){
    if(v == t){
        trap[v] = 1;
        return;
    }
    for(auto u : g[v])
        if(u != prt){
            dfs(u, v);
            if(trap[u])
                trap[v] = 1;
            else
                ++edgecnt[v];
        }
    dp[v] = edgecnt[v];
    for(auto u : g[v])
        if(u != prt && trap[u])
            dp[v] += dp[u];
}
int getans(int v, int prt, int curval){
    if(v == t) return 0;
    if(trap[v] == 0)
        curval -= edgecnt[v];
    if(curval < 0) return 1e9;
    vector<int> vec;
    for(auto u : g[v])
        if(u != prt && trap[u] == 0)
            vec.pb(getans(u, v, curval));
    int othneed = 0;
    for(auto u : g[v])
        if(u != prt && trap[u])
            othneed = getans(u, v, curval);
    sort(all(vec), greater<int>());
    int ret = 1e9;
    for(int i = 0; i < vec.size(); ++i)
        ret = min(ret, i+max(vec[i], othneed));
    ret = min(ret, (int)vec.size()+othneed);
    return max(ret-1, 0);
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);

    cin >> n >> t >> m;
    for(int i = 0; i < n-1; ++i){
        int x, y;
        cin >> x >> y;
        g[x].pb(y);
        g[y].pb(x);
    }
    dfs(m, 0);
    int l = 0, r = 1e9;
    while(l < r){
        int mid = (l+r)/2;
        if(getans(m, 0, mid-dp[m]) == 0)
            r = mid;
        else
            l = mid+1;
    }
    cout << l << '\n';
}

Compilation message (stderr)

mousetrap.cpp: In function 'int getans(int, int, int)':
mousetrap.cpp:54:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   54 |     for(int i = 0; i < vec.size(); ++i)
      |                    ~~^~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 0 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35