0
1
mirror of https://git.sb/baoshuo/OI-codes.git synced 2024-12-24 17:51:58 +00:00

P5331 [SNOI2019]通信

https://www.luogu.com.cn/record/100755482
This commit is contained in:
Baoshuo Ren 2023-01-29 15:16:21 +08:00
parent e53f61f527
commit f1147c9a2d
Signed by: baoshuo
GPG Key ID: 00CB9680AB29F51A

174
Luogu/P5331/P5331.cpp Normal file
View File

@ -0,0 +1,174 @@
#include <iostream>
#include <algorithm>
#include <cmath>
#include <iterator>
#include <queue>
#include <utility>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1005,
M = N * N;
const int INF = 0x3f3f3f3f;
int n, w, a[N], s, t, tot, pos1[N], pos2[N];
long long cost;
int idx, head[N << 4], ver[M << 5], next[M << 5];
std::pair<int, int> edge[M << 5];
int dist[N << 4];
bool vis[N << 4];
void add(int u, int v, int flow, int cost) {
next[idx] = head[u];
ver[idx] = v;
edge[idx] = std::make_pair(flow, cost);
head[u] = idx++;
}
bool spfa() {
std::fill(std::begin(vis), std::end(vis), false);
std::fill(std::begin(dist), std::end(dist), INF);
std::queue<int> q;
q.emplace(s);
dist[s] = 0;
vis[s] = true;
while (!q.empty()) {
int u = q.front();
q.pop();
vis[u] = false;
for (int i = head[u]; ~i; i = next[i]) {
int v = ver[i],
flow = edge[i].first,
cost = edge[i].second;
if (flow && dist[v] > dist[u] + cost) {
dist[v] = dist[u] + cost;
if (!vis[v]) {
q.emplace(v);
vis[v] = true;
}
}
}
}
return dist[t] != INF;
}
int dinic(int u, int limit) {
if (u == t) return limit;
int flow = 0;
vis[u] = true;
for (int i = head[u]; ~i && flow < limit; i = next[i]) {
int v = ver[i],
f = edge[i].first,
w = edge[i].second;
if (dist[v] == dist[u] + w && f && !vis[v]) {
int k = dinic(v, std::min(f, limit - flow));
if (!k) dist[v] = INF;
edge[i].first -= k;
edge[i ^ 1].first += k;
flow += k;
cost += k * w;
}
}
vis[u] = false;
return flow;
}
void solve(int l, int r) {
if (l == r) return;
int mid = (l + r) >> 1;
solve(l, mid);
solve(mid + 1, r);
std::vector<int> nums;
for (int i = l; i <= r; i++) {
nums.emplace_back(a[i]);
}
std::sort(nums.begin(), nums.end());
nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
for (int i = 0; i < nums.size() - 1; i++) {
add(tot + 1 + i, tot + 1 + i + 1, INF, nums[i + 1] - nums[i]);
add(tot + 1 + i + 1, tot + 1 + i, 0, -(nums[i + 1] - nums[i]));
add(tot + 1 + i + 1, tot + 1 + i, INF, nums[i + 1] - nums[i]);
add(tot + 1 + i, tot + 1 + i + 1, 0, -(nums[i + 1] - nums[i]));
}
for (int i = l; i <= r; i++) {
int pos = std::lower_bound(nums.begin(), nums.end(), a[i]) - nums.begin();
if (i <= mid) {
add(tot + 1 + pos, pos2[i], 1, 0);
add(pos2[i], tot + 1 + pos, 0, 0);
} else {
add(pos1[i], tot + 1 + pos, 1, 0);
add(tot + 1 + pos, pos1[i], 0, 0);
}
}
tot += nums.size();
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
std::fill(std::begin(head), std::end(head), -1);
cin >> n >> w;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
s = 0, t = ++tot;
for (int i = 1; i <= n; i++) {
pos1[i] = ++tot;
pos2[i] = ++tot;
// S -> i_1
add(s, pos1[i], 1, 0);
add(pos1[i], s, 0, 0);
// i_1 -> T
add(pos1[i], t, 1, w);
add(t, pos1[i], 0, -w);
// i_2 -> T
add(pos2[i], t, 1, 0);
add(t, pos2[i], 0, 0);
}
solve(1, n);
while (spfa()) {
while (dinic(s, INF)) {}
}
cout << cost << endl;
return 0;
}