Luogu P4015 运输问题
继续颓网络流\(hhhhh\),虽然这次写的是个大水题,但是早上水一个网络流果然还是让人心情舒畅啊~
最大费用最大流不用非得反着费用建边.只要没有正环,初始化的时候小心一点就好啦~
#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
int cnt = -1, head[210];
struct edge {
int nxt, to, w, f;
}e[40010];
void add_edge (int from, int to, int flw, int val) {
e[++cnt].nxt = head[from];
e[cnt].to = to;
e[cnt].f = flw;
e[cnt].w = val;
head[from] = cnt;
}
void add_len (int u, int v, int f, int w) {
add_edge (u, v, f, +w);
add_edge (v, u, 0, -w);
}
int _head[210]; edge _e[40010];
int n, m, numA[110], numB[110], cost[110][110];
int A (int x) {return n * 0 + x;}
int B (int x) {return n * 1 + x;}
queue <int> q;
int dis[210], vis[210], flow[210];
int pre_edge[210], pre_node[210];
bool can_use (int u, int v, int i, int type) {
if (type == +1) return dis[v] > dis[u] + e[i].w;
if (type == -1) return dis[v] < dis[u] + e[i].w;
}
int spfa (int s, int t, int type) {
memset (vis, 0, sizeof (vis));
memset (flow, 0x3f, sizeof (flow));
if (type == +1) memset (dis, +0x3f, sizeof (dis));
if (type == -1) memset (dis, -0x3f, sizeof (dis));
vis[s] = true; dis[s] = 0; q.push (s);
while (!q.empty ()) {
int u = q.front (); q.pop ();
for (int i = head[u]; ~i; i = e[i].nxt) {
int v = e[i].to;
if (can_use (u, v, i, type) && e[i].f) {
dis[v] = dis[u] + e[i].w;
flow[v] = min (flow[u], e[i].f);
pre_edge[v] = i;
pre_node[v] = u;
if (!vis[v]) {
vis[v] = true;
q.push (v);
}
}
}
vis[u] = false;
}
return flow[t] != INF;
}
int MCMF (int s, int t, int type) {
int cost = 0;
while (spfa (s, t, type)) {
cost += dis[t] * flow[t];
int u = t;
while (u != s) {
e[pre_edge[u] ^ 0].f -= flow[t];
e[pre_edge[u] ^ 1].f += flow[t];
u = pre_node[u];
}
}
return cost;
}
int main () {
memset (head, -1, sizeof (head));
cin >> n >> m;
int s = n + m + 1;
int t = n + m + 2;
for (int i = 1; i <= n; ++i) {cin >> numA[i]; add_len (s, A (i), numA[i], 0);}
for (int i = 1; i <= m; ++i) {cin >> numB[i]; add_len (B (i), t, numB[i], 0);}
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
cin >> cost[i][j];
add_len (A (i), B (j), INF, cost[i][j]);
}
}
memcpy (_e, e, sizeof (e)); memcpy (_head, head, sizeof (head));
cout << MCMF (s, t, +1) << endl;
memcpy (e, _e, sizeof (e)); memcpy (head, _head, sizeof (head));
cout << MCMF (s, t, -1) << endl;
}