結果
| 問題 |
No.1833 Subway Planning
|
| コンテスト | |
| ユーザー |
 Kude
|
| 提出日時 | 2022-02-04 23:53:38 |
| 言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
| 結果 |
AC
|
| 実行時間 | 284 ms / 4,000 ms |
| コード長 | 6,932 bytes |
| コンパイル時間 | 3,547 ms |
| コンパイル使用メモリ | 241,260 KB |
| 最終ジャッジ日時 | 2025-01-27 20:12:28 |
|
ジャッジサーバーID （参考情報） |
judge5 / judge5 |
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| ファイルパターン | 結果 |
|---|---|
| sample | AC * 3 |
| other | AC * 23 |
コンパイルメッセージ
In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23:
main.cpp:62:19: warning: ‘mi’ may be used uninitialized [-Wmaybe-uninitialized]
62 | assign_idx(mi, h, nxt, u);
| ~~~~~~~~~~^~~~~~~~~~~~~~~
main.cpp: In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’:
main.cpp:54:13: note: ‘mi’ was declared here
54 | int mi;
| ^~
In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23:
main.cpp:62:19: warning: ‘mi’ may be used uninitialized [-Wmaybe-uninitialized]
62 | assign_idx(mi, h, nxt, u);
| ~~~~~~~~~~^~~~~~~~~~~~~~~
main.cpp: In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’:
main.cpp:54:13: note: ‘mi’ was declared here
54 | int mi;
| ^~
In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:62:19,
inlined from ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’ at main.cpp:65:23:
main.cpp:62:19: warning: ‘mi’ may be used uninitialized [-Wmaybe-uninitialized]
62 | assign_idx(mi, h, nxt, u);
| ~~~~~~~~~~^~~~~~~~~~~~~~~
main.cpp: In member function ‘void {anonymous}::HLD::assign_idx(int, int, int&, int)’:
main.cpp:54:13: note: ‘mi’ was declared here
54 | int mi;
| ^~
In member
ソースコード
#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
struct HLD {
std::vector<std::vector<int>> &to;
int root, n;
std::vector<int> sz, parent, depth, idx, ridx, head, inv;
HLD(std::vector<std::vector<int>>& to, int root=0):
to(to), root(root), n(to.size()),
sz(n), parent(n), depth(n), idx(n), ridx(n), head(n), inv(n)
{
init_tree_data(root);
int x = 0;
assign_idx(root, root, x);
}
void init_tree_data(int u, int p=-1, int d=0) {
parent[u] = p;
depth[u] = d;
int s = 1;
for(int v: to[u]) {
if (v == p) continue;
init_tree_data(v, u, d+1);
s += sz[v];
}
sz[u] = s;
}
void assign_idx(int u, int h, int &nxt, int p=-1) {
head[u] = h;
inv[nxt] = u;
idx[u] = nxt++;
if (sz[u] == 1) {
ridx[u] = nxt;
return;
}
int mxsize = 0;
int mi;
for(int v: to[u]) {
if (v == p) continue;
if (sz[v] > mxsize) {
mxsize = sz[v];
mi = v;
}
}
assign_idx(mi, h, nxt, u);
for(int v: to[u]) {
if (v == p || v == mi) continue;
assign_idx(v, v, nxt, u);
}
ridx[u] = nxt;
}
int lca(int u, int v) {
while(head[u] != head[v]) {
if (depth[head[u]] > depth[head[v]]) u = parent[head[u]];
else v = parent[head[v]];
}
return (depth[u] < depth[v] ? u : v);
}
// returns (paths upto lca from x (excluding lca), those from y, lca)
std::tuple<std::vector<std::pair<int, int>>, std::vector<std::pair<int, int>>, int> paths(int x, int y) {
std::tuple<std::vector<std::pair<int, int>>, std::vector<std::pair<int, int>>, int> ret;
std::vector<std::pair<int, int>>& x_paths = get<0>(ret);
std::vector<std::pair<int, int>>& y_paths = get<1>(ret);
int& lca = get<2>(ret);
while(head[x] != head[y]) {
int xhead = head[x], yhead = head[y];
if (depth[xhead] > depth[yhead]) {
x_paths.emplace_back(x, xhead);
x = parent[xhead];
} else {
y_paths.emplace_back(y, yhead);
y = parent[yhead];
}
}
if (depth[x] > depth[y]) {
int ychild = inv[idx[y] + 1];
x_paths.emplace_back(x, ychild);
x = y;
} else if (depth[x] < depth[y]) {
int xchild = inv[idx[x] + 1];
y_paths.emplace_back(y, xchild);
y = x;
}
lca = x;
return ret;
}
int dist(int u, int v) {
int w = lca(u, v);
return depth[u] + depth[v] - 2 * depth[w];
}
};
template <class S, S (*op)(S, S)>
struct DisjointSparseTable {
const int n;
const vector<unsigned char> msb;
const vector<vector<S>> d;
DisjointSparseTable(vector<S> a) : n(a.size()), msb(build_msb_table(n)), d(build_table(move(a))) {}
vector<unsigned char> build_msb_table(int n) {
if (n <= 1) return {};
unsigned char k_max = 32 - __builtin_clz(n - 1);
vector<unsigned char> res(1 << k_max);
unsigned char* p = res.data();
for (unsigned char k = 0; k < k_max; k++) {
memset(p + (1U << k), k, 1U << k);
}
return res;
}
vector<vector<S>> build_table(vector<S> a) {
const int n = a.size();
vector<vector<S>> res(1);
if (n >= 2) {
const int i_max = n - 1, k_max = 32 - __builtin_clz(i_max);
res.resize(k_max);
for (int k = 1; k < k_max; k++) {
vector<S> t(i_max >> k & 1 ? n : i_max & ~0U << k);
for (int c = 1 << k; c < n; c += 1 << (k + 1)) {
int l = c - (1 << k);
int r = min(n, c + (1 << k));
t[c - 1] = a[c - 1];
for (int i = c - 2; i >= l; i--) t[i] = op(a[i], t[i + 1]);
t[c] = a[c];
for (int i = c + 1; i < r; i++) t[i] = op(t[i - 1], a[i]);
}
res[k] = move(t);
}
}
res[0] = move(a);
return res;
}
S query(int l, int r) { return query_closed(l, r - 1); }
S query_closed(int l, int r) {
assert(0 <= l && l <= r && r < n);
if (l == r) return d[0][l];
auto k = msb[l ^ r];
return op(d[k][l], d[k][r]);
}
};
int op_min(int x, int y) { return min(x, y); }
int op_max(int x, int y) { return max(x, y); }
} int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
struct E {
int a, b, c;
};
VVI to(n);
vector<E> es(n - 1);
for(auto& [a, b, c] : es) {
cin >> a >> b >> c;
a--, b--;
to[a].emplace_back(b);
to[b].emplace_back(a);
}
HLD hld(to);
VI init_vec(n);
for(auto& [a, b, c] : es) {
if (hld.depth[a] < hld.depth[b]) swap(a, b);
init_vec[hld.idx[a]] = c;
}
constexpr int INF = 1001001001;
DisjointSparseTable<int, op_min> RmQ(init_vec);
DisjointSparseTable<int, op_max> RMQ(init_vec);
vector<int> ord(n - 1);
iota(ord.begin(), ord.end(), 0);
sort(ord.begin(), ord.end(), [&](int i, int j) {
return es[i].c > es[j].c;
});
ord.emplace_back(n - 1);
es.push_back({-1, -1, -1});
int u = -1, v = -1;
int ans = INF;
rep(i, n - 1) {
auto [a, b, c] = es[ord[i]];
if (i == 0) {
u = a;
v = b;
} else {
int d = hld.dist(u, v);
if (hld.dist(a, u) + hld.dist(a, v) == d && hld.dist(b, u) + hld.dist(b, v) == d) {
;
} else {
int nu = -1, nv = -1;
if (hld.dist(a, u) > hld.dist(b, u)) nu = a;
else nu = b;
if (hld.dist(a, u) > hld.dist(a, v)) nv = u;
else nv = v;
int nd = hld.dist(nu, nv);
bool ok = true;
for (int t : {a, b, u, v}) {
if (hld.dist(t, nu) + hld.dist(t, nv) != nd) {
ok = false;
break;
}
}
if (!ok) break;
u = nu;
v = nv;
}
}
int mn = INF, mx = -INF;
auto [p1, p2, _] = hld.paths(u, v);
rep(_, 2) {
for (auto [x, y] : p1) {
int ix = hld.idx[x], iy = hld.idx[y];
chmin(mn, RmQ.query_closed(iy, ix));
chmax(mx, RMQ.query_closed(iy, ix));
}
swap(p1, p2);
}
chmin(ans, max(mx - mn, es[ord[i + 1]].c));
}
cout << ans << '\n';
}