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답안 #846676

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
846676 2023-09-08T08:51:49 Z vjudge1 Torrent (COI16_torrent) C++17
69 / 100
 317 ms 24820 KB 
#include <bits/stdc++.h>
#define task ""
#define fi first
#define se second
#define pii pair<int, int>

using namespace std;
using ll = long long;

const ll mod = 998244353;
const int inf = 1e9 + 1;
const int arr = 300001;

int n, a, b, dp[arr], child[arr];
vector<int> adj[arr];
vector<int> trace;
void findpath(int u, int p) {
    if(trace.empty() || trace.back() != b){
        trace.push_back(u);
    }
    for(auto v : adj[u]) if(v != p)
        findpath(v, u);
    if(trace.back() != b)
        trace.pop_back();
}
// bool cmp(int a, int b){
//     return a > b;
// }
void dfs(int u, int p){
    vector<int> time;
    dp[u] = 0;
    for(auto v : adj[u]){
        if(v != p && v != child[u]){
            dfs(v, u);
            time.push_back(dp[v]);
        }
    }
    sort(time.begin(), time.end(), greater<int>());
    for(int i = 0; i < time.size(); i++){
        dp[u] = max(dp[u], time[i] + i + 1); 
    }
}
pii calc(){  
    //memset(dp, 0, sizeof dp);
    dfs(a, 0);
    //memset(dp, 0, sizeof dp);
    dfs(b, 0);
    int ra = dp[a];
    int rb = dp[b];
    return {ra, rb};
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    // freopen(task".inp" , "r" , stdin);  
    // freopen(task".out" , "w" , stdout);
    cin >> n >> a >> b;
    for(int i = 1; i <= n; i++){
        int x, y; cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    findpath(a, 0);
    int l = 1, r = trace.size() - 1, res = 1e9;
    while(l <= r){
        int mid = (l + r) / 2;
        child[trace[mid]] = trace[mid - 1];
        child[trace[mid - 1]] = trace[mid];
        pii tmp = calc();
        child[trace[mid]] = child[trace[mid - 1]] = 0;
        res = min(res, max(tmp.fi, tmp.se));
        if(tmp.fi > tmp.se)r = mid - 1;
        else l = mid + 1;
    }
    cout << res << '\n';
}

Compilation message

torrent.cpp: In function 'void dfs(int, int)':
torrent.cpp:39:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for(int i = 0; i < time.size(); i++){
      |                    ~~^~~~~~~~~~~~~

Subtask #1
0 / 31.0

# 결과 실행 시간 메모리 Grader output
1 Incorrect 2 ms 8792 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #2
69.0 / 69.0

# 결과 실행 시간 메모리 Grader output
1 Correct 262 ms 21588 KB Output is correct
2 Correct 276 ms 22928 KB Output is correct
3 Correct 283 ms 24444 KB Output is correct
4 Correct 317 ms 23908 KB Output is correct
5 Correct 242 ms 21048 KB Output is correct
6 Correct 245 ms 21688 KB Output is correct
7 Correct 245 ms 24820 KB Output is correct