0
1
mirror of https://git.sb/baoshuo/OI-codes.git synced 2024-12-25 08:51:58 +00:00
OI-codes/S2OJ/366/366.cpp

159 lines
3.0 KiB
C++

#include <iostream>
#include <algorithm>
#include <iterator>
#include <queue>
#include <unordered_map>
#include <utility>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 55,
M = N * N * 4;
const int INF = 0x3f3f3f3f;
const std::unordered_map<char, std::pair<int, int>> d{
{'L', {0, -1}},
{'R', {0, 1}},
{'U', {-1, 0}},
{'D', {1, 0}},
};
int n, m, k, s, t, cnt, id[N][N], cost;
int idx, head[M], ver[M << 1], next[M << 1];
std::pair<int, int> edge[M << 1];
int dist[M];
bool vis[M];
void add(int u, int v, int c, int w) {
next[idx] = head[u];
ver[idx] = v;
edge[idx] = {c, w};
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],
c = edge[i].first,
w = edge[i].second;
if (c > 0 && dist[v] > dist[u] + w) {
dist[v] = dist[u] + w;
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],
c = edge[i].first,
w = edge[i].second;
if (dist[v] == dist[u] + w && c > 0 && !vis[v]) {
int k = dinic(v, std::min(c, 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;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
std::fill(std::begin(head), std::end(head), -1);
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
id[i][j] = ++cnt;
add(s, id[i][j], 1, 0);
add(id[i][j], s, 0, 0);
}
}
for (int i = 1; i <= k; i++) {
int x, y;
char d;
cin >> x >> y >> d;
x++, y++;
int xx = x + ::d.at(d).first,
yy = y + ::d.at(d).second,
p = ++cnt;
add(id[xx][yy], p, 1, 0);
add(p, id[xx][yy], 0, 0);
id[xx][yy] = ++cnt;
add(p, id[xx][yy], 1, 0);
add(id[xx][yy], p, 0, 0);
add(id[x][y], p, 1, -1);
add(p, id[x][y], 0, 1);
}
t = ++cnt;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
add(id[i][j], t, 1, 0);
add(t, id[i][j], 0, 0);
}
}
while (spfa() && dist[t] < 0) {
while (dinic(s, INF)) {}
}
cout << k + cost << endl;
return 0;
}