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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#284990 | #7936. Eliminate Tree | ucup-team1074# | WA | 12ms | 32544kb | C++23 | 4.5kb | 2023-12-16 16:06:18 | 2023-12-16 16:06:19 |
Judging History
answer
#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define pb push_back
#define x first
#define y second
#define endl '\n'
const LL maxn = 4e05+7;
const LL N = 5e05+10;
const LL mod = 1e09+7;
const int inf = 0x3f3f3f3f;
const LL llinf = 5e18;
typedef pair<int,int>pl;
priority_queue<LL , vector<LL>, greater<LL> >mi;//小根堆
priority_queue<LL> ma;//大根堆
LL gcd(LL a, LL b){
return b > 0 ? gcd(b , a % b) : a;
}
LL lcm(LL a , LL b){
return a / gcd(a , b) * b;
}
int n , m;
vector<int>a(N , 0);
void init(int n){
for(int i = 0 ; i <= n ; i ++){
a[i] = 0;
}
}
struct HLD {//轻重链剖分
int n;
std::vector<int> siz, top, dep, parent, in, out, seq;//子树大小 所在重链的顶部节点 深度 父亲 子树DFS序的起点 子树DFS序的终点
std::vector<std::vector<int>> adj;
int cur = 1;
HLD() {}
HLD(int n) {
init(n);
}
void init(int n) {
this->n = n;
siz.resize(n);
top.resize(n);
dep.resize(n);
parent.resize(n);
in.resize(n);
out.resize(n);
seq.resize(n);
cur = 1;
adj.assign(n, {});
}
void addEdge(int u, int v) {
adj[u].push_back(v);
adj[v].push_back(u);
}
void work(int root) {
top[root] = root;
dep[root] = 0;
parent[root] = -1;
dfs1(root);
dfs2(root);
}
void dfs1(int u) {
if (parent[u] != -1) {
adj[u].erase(std::find(adj[u].begin(), adj[u].end(), parent[u]));
}
siz[u] = 1;
for (auto &v : adj[u]) {
parent[v] = u;
dep[v] = dep[u] + 1;
dfs1(v);
siz[u] += siz[v];
if (siz[v] > siz[adj[u][0]]) {
std::swap(v, adj[u][0]);
}
}
}
void dfs2(int u) {
in[u] = ++cur;
seq[in[u]] = u;
for (auto v : adj[u]) {
top[v] = v == adj[u][0] ? top[u] : v;
dfs2(v);
}
out[u] = cur;
}
int lca(int u, int v) {
while (top[u] != top[v]) {
if (dep[top[u]] > dep[top[v]]) {
u = parent[top[u]];
} else {
v = parent[top[v]];
}
}
return dep[u] < dep[v] ? u : v;
}
int dist(int u, int v) {
return dep[u] + dep[v] - 2 * dep[lca(u, v)];
}
int jump(int u, int k) {
if (dep[u] < k) {
return -1;
}
int d = dep[u] - k;
while (dep[top[u]] > d) {
u = parent[top[u]];
}
return seq[in[u] - dep[u] + d];
}
bool isAncester(int u, int v) {//是否为祖先
return in[u] <= in[v] && in[v] < out[u];
}
int rootedParent(int u, int v) {
std::swap(u, v);
if (u == v) {
return u;
}
if (!isAncester(u, v)) {
return parent[u];
}
auto it = std::upper_bound(adj[u].begin(), adj[u].end(), v, [&](int x, int y) {
return in[x] < in[y];
}) - 1;
return *it;
}
int rootedSize(int u, int v) {
if (u == v) {
return n;
}
if (!isAncester(v, u)) {
return siz[v];
}
return n - siz[rootedParent(u, v)];
}
int rootedLca(int a, int b, int c) {
return lca(a, b) ^ lca(b, c) ^ lca(c, a);
}
}hld;
vector<vector<int>>dp(N , vector<int>(2 , 0));//不保留or保留
void dfs(int u){
dp[u][0] = dp[u][1] = 0;
for(auto v : hld.adj[u]){
dfs(v);
dp[u][1] += dp[v][0];
}
dp[u][0] = dp[u][1] + 2;
for(auto v : hld.adj[u]){
dp[u][0] = min(dp[u][0] , dp[u][1] - dp[v][0] + dp[v][1] + 1);
}
}
void solve()
{
cin >> n;
hld.init(n + 5);
vector<int>deg(n + 5 , 0);
for(int i = 1 ; i < n ; i ++){
int u , v;
cin >> u >> v;
deg[u]++;
deg[v]++;
hld.addEdge(u , v);
}
int maxx = 0;
for(int i = 1 ; i <= n ; i++){
maxx = max(maxx , deg[i]);
}
if(maxx == 0){
cout << 0 << endl;
}
else if(maxx <= 2){
cout << (n - 1) / 2 << endl;
}
else{
int root = 1;
hld.work(root);
dfs(root);
cout << dp[root][0] << endl;
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cout.precision(10);
int t=1;
// cin>>t;
while(t--)
{
solve();
}
return 0;
}
Details
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Test #1:
score: 100
Accepted
time: 12ms
memory: 32544kb
input:
5 1 2 2 3 3 4 3 5
output:
4
result:
ok 1 number(s): "4"
Test #2:
score: -100
Wrong Answer
time: 9ms
memory: 32172kb
input:
4 1 2 2 3 3 4
output:
1
result:
wrong answer 1st numbers differ - expected: '2', found: '1'