bzoj 1006: 神奇的国度 MCS

题目大意:

弦图的最小染色.

题解:

裸题.

#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
inline void read(int &x){
    x=0;static char ch;bool flag = false;
    while(ch=getchar(),ch<'!');if(ch == '-') ch=getchar(),flag = true;
    while(x=10*x+ch-'0',ch=getchar(),ch>'!');if(flag) x=-x;
}
#define rg register int
#define rep(i,a,b) for(rg i=(a);i<=(b);++i)
#define per(i,a,b) for(rg i=(a);i>=(b);--i)
const int maxn = 10010;
const int maxm = 1000010;
struct Edge{
    int to,next;
}G[maxm<<1];
int head[maxn],cnt;
void add(int u,int v){
    G[++cnt].to = v;
    G[cnt].next = head[u];
    head[u] = cnt;
}
vector<int>ws[maxn];
int seq[maxn],pos[maxn],fla[maxn],col[maxn];
int lab[maxn];
int main(){
    int n,m;read(n);read(m);
    int u,v;
    rep(i,1,m){
        read(u);read(v);
        add(u,v);add(v,u);
    }
    int nw = 0,ans = 0;
    rep(i,1,n) ws[0].push_back(i);
    per(i,n,1){
        while(1){
            u = ws[nw].back();
            if(pos[u]) ws[nw].pop_back();
            else break;
            while(ws[nw].empty()) -- nw;
        }
        seq[i] = u;pos[u] = i;
        for(int p = head[u];p;p=G[p].next){
            fla[ col[ G[p].to ] ] = i;
            ++ lab[G[p].to];
            nw = max(nw,lab[G[p].to]);
            ws[lab[G[p].to]].push_back(G[p].to);
        }
        rep(j,1,n){
            if(fla[j] != i){
                col[u] = j;
                ans = max(ans,j);
                break;
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}