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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#758924 | #9570. Binary Tree | wht11 | TL | 2ms | 5852kb | C++20 | 4.8kb | 2024-11-17 20:27:34 | 2024-11-17 20:27:34 |
Judging History
answer
#include <bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
using PII = pair<int, int>;
#define endl "\n"
const int N = 2e5 + 5;
vector<int> G[N];
int siz[N], f[N], vis[N], cnt[N];
int lst = 0;
int mid = 0;
void dfs(int u, int fa)
{
f[u] = fa;
siz[u] = 1;
int flag=1;
for (auto v : G[u])
{
if (v == fa || vis[v])
continue;
dfs(v, u);
if(siz[v]>lst/2) flag=0;
siz[u] += siz[v];
}
if (vis[u])
return;
if(lst-siz[u]>lst/2) flag=0;
if (flag)
mid = u;
}
void del(int u, int fa)
{
vis[u] = 1;
cnt[u]--;
cnt[fa]--;
siz[u] = 1;
for (auto v : G[u])
{
if (v == fa || vis[v])
continue;del(v, u);
siz[u] += siz[v];
}
}
void solve()
{
int n;
cin >> n;
for (int i = 1; i <= n; i++)
{
G[i].clear();
vis[i] = 0;
f[i] = 0;
siz[i] = 0;
cnt[i]=0;
}
for (int i = 1; i <= n; i++)
{
int u, v;
cin >> u >> v;
if (v)
{
G[i].push_back(v);
G[v].push_back(i);
cnt[i]++;
cnt[v]++;
}
if (u)
{
G[i].push_back(u);
G[u].push_back(i);
cnt[i]++;
cnt[u]++;
}
}
lst = n;
int rt = 1;
mid = 0;
while (1)
{
if(lst==1) {
cout << "! " << rt << endl;
cout.flush();
return;
}
int x;
mid = rt;
dfs(rt, 0);
if (cnt[mid] == 3)
{
vector<pair<int, int>> ve;
for (auto v : G[mid])
{
if (vis[v])
continue;
if (v == f[mid])
ve.emplace_back(lst - siz[mid], v);
else
ve.emplace_back(siz[v], v);
}
sort(ve.begin(), ve.end(), greater<pair<int, int>>());
int mx1 = 0, mx2 = 0;
int mx11 = 0, mx22 = 0;
for (auto tmp : ve)
{
int val = tmp.first;
int v = tmp.second;
if (val > mx1)
{
mx2 = mx1;
mx1 = val;
mx22 = mx11;
mx11 = v;
}
else if (val > mx2)
{
mx2 = val;
mx22 = v;
}
}
cout << "? " << mx11 << " " << mx22 << endl;
cout.flush();
cin >> x;
if (x == 0)
{
del(mid, mx11);
lst -= siz[mid];
rt = mx11;
}
else if (x == 1)
{
del(mx22, mid);
lst -= siz[mx22];
del(mx11, mid);
lst -= siz[mx11];
rt = mid;
}
else
{
del(mid, mx22);
lst -= siz[mid];
rt = mx22;
}
}
else if (cnt[mid] == 2)
{
vector<int> ve;
for (auto v : G[mid])
{
if (vis[v])
continue;
ve.push_back(v);
}
cout << "? " << ve[0] << " " << ve[1] << endl;
cout.flush();
cin >> x;
if (x == 0)
{
del(mid, ve[0]);
lst -= siz[mid];
rt = ve[0];
}
else if (x == 1)
{
cout << "! " << mid << endl;
return;
}
else
{
del(mid, ve[1]);
lst -= siz[mid];
rt = ve[1];
}
}
else if (cnt[mid] == 1)
{
int xx;
for (auto v : G[mid])
{
if (vis[v])
continue;
xx=v;
}
cout << "? " << mid <<" " << xx << endl;
cout.flush();
cin >>x;
if(x==1)
{
cout << "! " << mid << endl;
cout.flush();
}
else if(x==2)
{
cout << "! " <<xx<< endl;
cout.flush();
}
else
{
cout << "! " <<mid<< endl;
cout.flush();
}
return;
}
else
{
cout << "! " << rt << endl;
cout.flush();
return;
}
}
}
signed main()
{
IOS;
int t = 1;
cin >> t;
while (t--)
{
solve();
}
return 0;
}
Details
Tip: Click on the bar to expand more detailed information
Test #1:
score: 100
Accepted
time: 2ms
memory: 5852kb
input:
2 5 0 0 1 5 2 4 0 0 0 0 1 0 2 0 2 0 0 2
output:
? 3 5 ? 2 1 ! 2 ? 1 2 ! 2
result:
ok OK (2 test cases)
Test #2:
score: -100
Time Limit Exceeded
input:
5555 8 2 0 8 6 0 0 3 0 0 0 7 0 0 0 5 4 0 0 2 8 0 0 1 4 2 0 0 0 7 8 0 0 3 0 6 0 2 0 0 8 5 8 0 0 1 7 0 0 0 0 4 2 0 0 6 0 0 1 2 5 4 5 3 1 0 0 0 0 0 0 0 2 8 0 0 0 0 5 6 0 0 1 4 2 0 3 8 0 0 0 0 5 3 0 5 1 0 0 0 0 4 0 0 2 5 5 0 0 0 0 0 3 0 2 4 0 0 3 3 0 1 0 0 0 2 2 2 0 0 0 0 3 2 3 0 0 0 0 2 10 2 8 9 7 0 0 ...
output:
? 8 6 ? 4 5 ? 4 3 ! 3 ? 2 7 ? 8 7 ? 8 6 ! 8 ? 8 3 ? 8 4 ? 6 2 ! 2 ? 2 5 ? 2 3 ! 3 ? 5 7 ? 4 1 ! 4 ? 1 5 ? 1 3 ! 3 ? 4 2 ? 4 3 ! 4 ? 3 2 ! 2 ? 1 2 ! 1 ? 3 2 ! 2 ? 7 9 ? 7 4 ? 6 3 ! 3 ? 1 2 ! 1 ? 5 9 ? 8 5 ? 3 4 ! 3 ? 10 3 ? 8 6 ? 4 2 ! 4 ? 9 3 ? 9 7 ? 2 1 ! 2 ? 1 2 ! 2 ? 4 3 ? 1 7 ! 7 ? 4 9 ? 8 4 ? 8...