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https://git.sb/baoshuo/OI-codes.git
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134 lines
2.7 KiB
C++
134 lines
2.7 KiB
C++
#include <iostream>
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#include <cstring>
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#include <queue>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 5005,
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M = 100005,
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INF = 0x3f3f3f3f;
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int n, k, s, t, ans;
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// Graph
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int idx, head[N], ver[M << 1], next[M << 1];
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std::pair<int, int> edge[M << 1];
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// <flow, cost>
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void add(int u, int v, int flow, int cost) {
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next[idx] = head[u];
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ver[idx] = v;
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edge[idx] = std::make_pair(flow, cost);
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head[u] = idx++;
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}
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inline int id(int i, int j, int k = 0) {
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return (i - 1) * n + j + k * n * n;
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}
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// Dinic
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int dist[N];
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bool vis[N];
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bool spfa() {
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memset(vis, 0x00, sizeof(vis));
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memset(dist, 0x3f, sizeof(dist));
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std::queue<int> q;
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q.push(s);
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dist[s] = 0;
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vis[s] = true;
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while (!q.empty()) {
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int u = q.front();
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q.pop();
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vis[u] = false;
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for (int i = head[u]; ~i; i = next[i]) {
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int v = ver[i],
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c = edge[i].first,
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w = edge[i].second;
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if (c > 0 && dist[v] > dist[u] + w) {
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dist[v] = dist[u] + w;
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if (!vis[v]) {
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q.push(v);
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vis[v] = true;
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}
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}
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}
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}
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return dist[t] != INF;
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}
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int dinic(int u, int limit) {
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if (u == t) return limit;
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int flow = 0;
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vis[u] = true;
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for (int i = head[u]; ~i && flow < limit; i = next[i]) {
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int v = ver[i],
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c = edge[i].first,
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w = edge[i].second;
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if (dist[v] == dist[u] + w && c && !vis[v]) {
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int k = dinic(v, std::min(c, limit - flow));
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if (!k) dist[v] = INF;
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edge[i].first -= k;
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edge[i ^ 1].first += k;
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flow += k;
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ans += k * w;
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}
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}
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vis[u] = false;
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return flow;
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}
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int main() {
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std::ios::sync_with_stdio(false);
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memset(head, 0xff, sizeof(head));
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cin >> n >> k;
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s = 0;
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add(s, id(1, 1), k, 0);
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add(id(1, 1), s, 0, 0);
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t = id(n, n, 1) + 1;
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add(id(n, n, 1), t, k, 0);
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add(t, id(n, n, 1), 0, 0);
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= n; j++) {
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int w;
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cin >> w;
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add(id(i, j), id(i, j, 1), 1, -w);
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add(id(i, j, 1), id(i, j), 0, w);
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add(id(i, j), id(i, j, 1), INF, 0);
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add(id(i, j, 1), id(i, j), 0, 0);
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if (i < n) {
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add(id(i, j, 1), id(i + 1, j), INF, 0);
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add(id(i + 1, j), id(i, j, 1), 0, 0);
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}
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if (j < n) {
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add(id(i, j, 1), id(i, j + 1), INF, 0);
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add(id(i, j + 1), id(i, j, 1), 0, 0);
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}
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}
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}
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while (spfa()) dinic(s, INF);
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cout << -ans << endl;
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return 0;
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}
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