2019 ccpc秦皇岛

1006 （dfs）

#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const double eps = 1e-6;
const int N = 3e5+7;
typedef long long ll;
const ll mod = 998244353 ;
using namespace std;
vector<int> G[N];
int d[N],vis[N];
ll qpow(ll a,ll b){
    ll ans=1; ll base=a;
    while(b){
        if(b&1) ans=ans*base%mod;
        base=base*base%mod;
        b>>=1;
    }
    return ans;
}
ll res=1;
ll num=0;
void dfs(int u,int fa,int cnt){
    //cout<<u<<endl;
    d[u]=cnt;
    for(int i=0;i<G[u].size();i++){
        int v=G[u][i];
        if(v==fa) continue; 
        if(!vis[v]){
            vis[v]=1;
            dfs(v,u,cnt+1);
            vis[v]=2; 
        }else if(vis[v]==1){
            //cout<<cnt-d[v]+1<<endl;
            res=res*(qpow(2,cnt-d[v]+1)-1)%mod;
            num+=(cnt-d[v]+1);
        }else if(vis[v]==2){
        }
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    int n,m;
    while(cin>>n>>m){
        for(int i=1;i<=n;i++) G[i].clear();
        memset(vis,0,sizeof(vis));
        memset(d,0,sizeof(d));
        res=1;
        num=0;
        for(int i=1;i<=m;i++){
            int u,v; cin>>u>>v;
            G[u].push_back(v);
            G[v].push_back(u); 
        }
        vis[1]=1;
        dfs(1,0,1);
    //    for(int i=1;i<=n;i++)
    //        cout<<d[i]<<endl;
    //    cout<<res<<endl;
        //cout<<num<<endl;
        cout<<res*qpow(2,m-num)%mod<<endl;
    }
    return 0;
}

1010（kmp）

#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const double eps = 1e-6;
const int N = 1e7+7 ;
typedef long long ll;
const ll mod = 998244353 ;
using namespace std;
int nextt[N];
void get_next(string s){
    nextt[1]=0;
    int len=s.length();
    for(int i=2,j=0;i<=len;i++){
        while(j>0&&s[j]!=s[i-1]) j=nextt[j];
        if(s[j]==s[i-1]) j++;
        nextt[i]=j;
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    ll a,b;
    while(cin>>a>>b){
        string s; cin>>s;
        int len=s.length();
        int po=0;
        for(int i=0;i<len;i++){
            if(s[i]=='.'){
                po=i;
                break;
            }
        }
        s=s.substr(po+1,len-po-1);
        reverse(s.begin(),s.end());
        get_next(s);
        len=s.length();
        ll ans=-inf;
        for(int i=1;i<=len;i++){
            ans=max(ans,a*i-b*(i-nextt[i]));
        }
        cout<<ans<<endl;
    } 
    return 0;
}