[BZOJ1006][[HNOI2008]神奇的国度][MCS，完美消除序列]

[BZOJ1006][[HNOI2008]神奇的国度][MCS，完美消除序列]

题目大意：

思路：

代码：

#include <bits/stdc++.h>
#define F(x) (x + n + 1)
const int Maxn = 10005;
const int Maxm = 1000050;
using namespace std;
namespace IO {
inline char get(void) {
static char buf[1000000], *p1 = buf, *p2 = buf;
if (p1 == p2) {
p2 = (p1 = buf) + fread(buf, 1, 1000000, stdin);
if (p1 == p2) return EOF;
}
return *p1++;
}
inline void read(int &x) {
x = 0; static char c;
for (; !(c >= '0' && c <= '9'); c = get());
for (; c >= '0' && c <= '9'; x = x * 10 + c - '0', c = get());
}
};
int n, m;
int head[Maxn << 1], sub;
struct Edge {
int to, nxt;
Edge(void) {}
Edge(const int &to, const int &nxt) : to(to), nxt(nxt) {}
} edge[Maxm << 1];
inline int add(int a, int b) {
edge[++sub] = Edge(b, head[a]), head[a] = sub;
}
int best, f[Maxn], seq[Maxn];
bool vis[Maxn];
inline int Max(const int &a, const int &b) {
return a > b ? a : b;
}
inline void MCS(void) {
int V;
for (int i = n; i; i--) {
V = 0;
for (int j = 1; j <= n; j++)
if (!vis[j] && f[j] >= f[V]) V = j;
vis[V] = 1; seq[i] = V;
for (int j = head[V], v; j; j = edge[j].nxt) {
v = edge[j].to;
f[v]++;
}
}
}
int xx[Maxn];
inline void color(int u) {
for (int i = head[u], v; i; i = edge[i].nxt) {
v = edge[i].to;
if (f[v] == -1) continue;
xx[f[v]] = u;
}
for (int i = 1; f[u] == -1; i++)
if (xx[i] != u) f[u] = i;
}
int main(void) {
//freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
IO::read(n), IO::read(m);
for (int i = 1; i <= m; i++) {
int a, b;
IO::read(a), IO::read(b);
add(a, b), add(b, a);
}
MCS();

memset(f, -1, sizeof f);
memset(xx, -1, sizeof xx);
for (int i = n; i; i--) color(seq[i]);
int ans = 0;
for (int i = 1; i <= n; i++) ans = Max(ans, f[i]);
cout << ans << endl;
return 0;
}