BZOJ 1070: [SCOI2007]修车

/*
BZOJ 1070: [SCOI2007]修车

费用流

i,j写反，调了一下午
lqz已经废了

*/
#include <cstdio>
#include <iostream>
#define rg register
inline void read (int &n) {
rg char c = getchar ();
for (n = 0; !isdigit (c); c = getchar ());
for (; isdigit (c); n = n * 10 + c - '0', c = getchar ());
}
int S, T;
#define Max 7000
#define INF 1e9
namespace net {
const int MaxE = 200000;
int _n[MaxE], _v[MaxE], list[Max], _f[MaxE], _c[MaxE], EC = 1, d[Max], q[MaxE], pre[Max];
bool is[Max]; int c[Max];
inline void In (int u, int v, int f, int c) {
_v[++ EC] = v, _n[EC] = list[u], list[u] = EC, _f[EC] = f, _c[EC] = c;
_v[++ EC] = u, _n[EC] = list[v], list[v] = EC, _f[EC] = 0, _c[EC] = -c;
}

bool Bfs () {
int h = 1, t = 1; q[t] = S; rg int i, n;
for (i = 0; i <= T; ++ i) d[i] = INF, is[i] = false;
for (d[S] = 0, c[S] = INF, pre[S] = 0; h <= t; ++ h)
for (n = q[h], is
= false, i = list
; i; i = _n[i])
if (d[_v[i]] > d
+ _c[i] && _f[i]) {
d[_v[i]] = d
+ _c[i], pre[_v[i]] = i, c[_v[i]] = std :: min (c
, _f[i]);
if (!is[_v[i]]) q[++ t] = _v[i], is[_v[i]] = true;
}
return d[T] < INF;
}
int Do () {
int res = 0; rg int i;
for (int x; Bfs (); ) {
for (x = c[T], i = T; i != S; i = _v[pre[i] ^ 1])
_f[pre[i]] -= x, _f[pre[i] ^ 1] += x;
res += d[T] * x;
}
return res;
}
}
int a[Max / 100][Max / 100];
int main (int argc, char *argv[]) {
int N, M; read (M), read (N); rg int i, j, k;
S = 0, T = N * M * 2;
for (i = 1; i <= N; ++ i)
for (j = 1; j <= M; ++ j) read (a[j][i]);
for (i = 1; i <= M; ++ i)
for (j = 1; j <= N; ++ j) net :: In ((i - 1) * N + j, T, 1, 0);
for (i = 1; i <= N; ++ i) net :: In (S, N * M + i, 1, 0);
for (i = 1; i <= N; ++ i)
for (j = 1; j <= M; ++ j)
for (k = 1; k <= N; ++ k)
net :: In (N * M + i, (j - 1) * N + k, 1, k * a[j][i]);
int res = net :: Do ();
printf ("%.2lf", (double) res / N);
return 0;
}