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QOJ
ID | 题目 | 提交者 | 结果 | 用时 | 内存 | 语言 | 文件大小 | 提交时间 | 测评时间 |
---|---|---|---|---|---|---|---|---|---|
#503590 | #7613. Inverse Problem | pandapythoner | ML | 1ms | 3920kb | C++23 | 7.6kb | 2024-08-03 20:26:51 | 2024-08-03 20:26:51 |
Judging History
answer
#pragma GCC optimize("Ofast,unroll-loops,fast-math")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define flt double
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define rep(i, n) for(int i = 0; i < n; i += 1)
#define len(a) ((int)(a).size())
const ll inf = 1e18;
mt19937 rnd(234);
const ll mod = 1e9 + 7;
ll bin_pow(ll x, ll n) {
ll rs = 1;
for (ll a = x, i = 1; i <= n; i *= 2, a = (a * a) % mod)
if (n & i) rs = rs * a % mod;
return rs;
}
ll inv(ll x) {
ll a = bin_pow(x, mod - 2);
assert(a * x % mod == 1);
return a;
}
vector<pair<int, int>> restore_tree(vector<int> degs) {
int n = len(degs);
vector<pair<int, int>> edges;
set<pair<int, int>> st;
int sum = 0;
rep(i, n) {
sum += degs[i];
st.insert(make_pair(degs[i], i));
}
assert(sum == 2 * n - 2);
while (!st.empty()) {
assert(len(st) >= 2);
auto [du, u] = *st.begin();
st.erase(st.begin());
auto [dv, v] = *prev(st.end());
st.erase(prev(st.end()));
assert(du == 1);
edges.push_back(make_pair(u, v));
assert(st.empty() or dv > 1);
if (dv > 1)
st.insert(make_pair(dv - 1, v));
}
return edges;
}
const int maxn = 200;
vector<ll> dp_pref[maxn][maxn], dp_suff[maxn][maxn];
int32_t main() {
if (1) {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int t;
cin >> t;
vector<ll> a(t);
rep(i, t) cin >> a[i];
vector<bool> is_solved(t, false);
vector<vector<pair<int, int>>> trees(t);
rep(i, t) {
if (a[i] == 1) {
trees[i] = {};
is_solved[i] = true;
} else if (a[i] == 2) {
trees[i] = { make_pair(0, 1) };
is_solved[i] = true;
}
}
for (ll n = 3; ; n += 1) {
if (all_of(all(is_solved), identity())) {
break;
}
cerr << n << "\n";
assert(n < maxn);
vector<ll> factors(n - 1);
factors[0] = 1;
for (int i = 1; i <= n - 2; i += 1) {
factors[i] = (factors[i - 1] * (n - 1 - i)) % mod;
}
vector<ll> inv_factors(n - 1);
rep(i, n - 1) inv_factors[i] = inv(factors[i]);
int max_pref_sum = (n - 2) / 3;
int max_suff_sum = n - 2 - max_pref_sum - 1;
rep(x, n - 1) rep(y, n - 1) dp_pref[x][y] = dp_suff[x][y] = {};
for (int val = 1; val <= n - 2; val += 1) {
dp_pref[val][0] = { factors[val] };
for (int sum = 1; val + sum <= n - 2 and sum <= max_pref_sum; sum += 1) {
int sum_size = 0;
for (int old_val = 1; old_val <= sum and old_val <= val; old_val += 1) {
sum_size += len(dp_pref[old_val][sum - old_val]);
}
dp_pref[val][sum].reserve(sum_size);
for (int old_val = 1; old_val <= sum and old_val <= val; old_val += 1) {
for (auto x : dp_pref[old_val][sum - old_val]) {
dp_pref[val][sum].push_back(x * factors[val] % mod);
}
}
sort(all(dp_pref[val][sum]));
dp_pref[val][sum].resize(unique(all(dp_pref[val][sum])) - dp_pref[val][sum].begin());
}
}
auto restore_pref = [&](int val, int sum, ll x) {
assert(binary_search(all(dp_pref[val][sum]), x));
vector<int> result;
result.push_back(val);
while (sum > 0) {
int new_val = -1;
x = x * inv_factors[val] % mod;
for (int old_val = 1; old_val <= sum and old_val <= val; old_val += 1) {
if (binary_search(all(dp_pref[old_val][sum - old_val]), x)) {
new_val = old_val;
break;
}
}
assert(new_val != -1);
val = new_val;
sum -= val;
result.push_back(val);
}
return result;
};
for (int val = n - 2; val >= 1; val -= 1) {
dp_suff[val][0] = { 1 };
for (int sum = 1; val + sum <= n - 2 and sum <= max_suff_sum; sum += 1) {
int sum_size = 0;
for (int old_val = val; old_val <= sum; old_val += 1) {
sum_size += len(dp_suff[old_val][sum - old_val]);
}
dp_suff[val][sum].reserve(sum_size);
for (int old_val = val; old_val <= sum; old_val += 1) {
for (auto x : dp_suff[old_val][sum - old_val]) {
dp_suff[val][sum].push_back(x * inv_factors[old_val] % mod);
}
}
// sort(all(dp_suff[val][sum]));
// dp_suff[val][sum].resize(unique(all(dp_suff[val][sum])) - dp_suff[val][sum].begin());
}
}
auto restore_suff = [&](int val, int sum, ll x) {
assert(find(all(dp_suff[val][sum]), x) != dp_suff[val][sum].end());
vector<int> result;
while (sum > 0) {
int new_val = -1;
for (int old_val = val; old_val <= sum; old_val += 1) {
if (find(all(dp_suff[old_val][sum - old_val]), x * factors[old_val] % mod) != dp_suff[old_val][sum - old_val].end()) {
new_val = old_val;
break;
}
}
assert(new_val != -1);
x = x * factors[new_val] % mod;
val = new_val;
sum -= val;
result.push_back(val);
}
return result;
};
ll d = n * (n - 1) % mod;
ll invd = inv(d);
for (int pref_sum = 0; pref_sum <= max_pref_sum; pref_sum += 1) {
for (int val = 1; pref_sum + val <= n - 2; val += 1) {
if (pref_sum + val <= max_pref_sum) continue;
int suff_sum = n - 2 - pref_sum - val;
assert(suff_sum <= max_suff_sum);
if (dp_pref[val][pref_sum].empty() or dp_suff[val][suff_sum].empty()) continue;
rep(i, t) if (!is_solved[i]) {
ll biba = a[i] * invd % mod;
for (auto y : dp_suff[val][suff_sum]) {
ll x = biba * y % mod;
if (binary_search(all(dp_pref[val][pref_sum]), x)) {
vector<int> degs_pref = restore_pref(val, pref_sum, x);
vector<int> degs_suff = restore_suff(val, suff_sum, y);
auto degs = degs_pref;
for (auto f : degs_suff) {
degs.push_back(f);
}
assert(len(degs) <= n - 2);
degs.resize(n, 0);
for (auto& f : degs) f += 1;
trees[i] = restore_tree(degs);
is_solved[i] = true;
break;
}
}
}
}
}
}
for (auto tree : trees) {
int n = len(tree) + 1;
cout << n << "\n";
for (auto [u, v] : tree) {
cout << u + 1 << " " << v + 1 << "\n";
}
}
return 0;
}
/*
9
185396120
468170792
837583517
696626231
338497514
762842660
800028852
928391161
733524004
*/
詳細信息
Test #1:
score: 100
Accepted
time: 1ms
memory: 3920kb
input:
4 2 360 1 509949433
output:
2 1 2 5 3 1 4 2 2 1 1 5 1 10 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 10
result:
ok OK (4 test cases)
Test #2:
score: -100
Memory Limit Exceeded
input:
9 185396120 468170792 837583517 696626231 338497514 762842660 800028852 928391161 733524004
output:
14 11 10 12 9 13 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 14 122 27 26 28 26 29 25 30 26 31 25 32 26 33 25 34 26 35 25 36 26 37 25 38 26 39 25 40 26 41 25 42 26 43 25 44 26 45 25 46 26 47 25 48 26 49 25 50 26 51 25 52 26 53 25 54 26 55 25 56 26 57 25 58 26 59 25 60 26 61 25 62 26 63 25 64 26 65 25 ...