Codeforces - 1105F Helping Hiasat（最大独立集）

传送门：Codeforces - 1105F

思路分析

对于每一个1操作，之后的2操作只能选择一个，将1操作之后的所有连边，答案就是求最大独立集
最大独立集又是补图的最大团

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (int)(x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;

const int INF = 0x3f3f3f3f;
const int N = 44;

int n,m;
map<string,int>MP;
int cnt,num[N],ans_s[N],now_s[N],e[N][N],ans;

int dfs(int u,int siz) {
    for(int v = u+1; v<=n; v++) {
        if(num[v]+siz<=ans) return 0;
        if(e[u][v]) {
            int ok = 1;
            for(int i=1; i<=siz; i++) {
                if(!e[v][now_s[i]]) {
                    ok = 0;
                    break;
                }
            }
            if(ok){
                now_s[siz+1] = v;
                if(dfs(v,siz+1)) return 1;
            }
        }
    }
    if(siz>ans){
        ans = siz;
        for(int i=1;i<=siz;i++) ans_s[i] = now_s[i];
        return 1;
    }
    return 0;
}

void maxclique(){
    ans = -1;
    for(int i=n;i>=1;i--){
        now_s[1] = i;
        dfs(i,1);
        num[i] = ans;
    }
}

signed main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    cin>>n>>m;
    vector<int>tmp;
    for(int i=1; i<=m; i++) for(int j=1; j<=m; j++) e[i][j] = 1;
    for(int i=1; i<=n; i++) {
        int op;
        string s;
        cin>>op;
        if(op == 1) tmp.clear();
        else {
            cin>>s;
            if(!MP[s]) MP[s] = ++cnt;
            int u = MP[s];
            for(auto v:tmp) e[u][v] = e[v][u] = 0;
            tmp.pb(u);
        }
    }
    n = m;
    maxclique();
    cout<<ans<<endl;






    return 0;
}


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