Codeforces Round #257 (Div. 2)

Codeforces Round #257 (Div. 2)

https://codeforces.com/contest/450/

A

模拟

#include<bits/stdc++.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define sqr(x) ((x)*(x))
#define pb push_back
#define eb emplace_back
#define maxn 100005
#define eps 1e-8
#define pi acos(-1.0)
#define rep(k,i,j) for(int k=i;k<j;k++)
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<long long,int>pli;
typedef pair<int,char> pic;
typedef pair<pair<int,string>,pii> ppp;
typedef unsigned long long ull;
const long long MOD=1e9+7;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int n,m;
int a[105];

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    cin>>n>>m;
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    int pos=0;
    int i=0;
    int co=0;
    while(1){
        if(a[i]>0){
            pos=i;
            a[i]-=min(m,a[i]);
            co=0;
        }
        else {
            co++;
        }
        i=(i+1)%n;
        if(co==n) break;
    }
    cout<<pos+1<<endl;

}

 

B

矩阵快速幂

#include<bits/stdc++.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define sqr(x) ((x)*(x))
#define pb push_back
#define eb emplace_back
#define maxn 100005
#define eps 1e-8
#define pi acos(-1.0)
#define rep(k,i,j) for(int k=i;k<j;k++)
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<long long,int>pli;
typedef pair<int,char> pic;
typedef pair<pair<int,string>,pii> ppp;
typedef unsigned long long ull;
const long long mod=1e9+7;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */
ll n,m,k;
struct sair{
    ll a[3][3];
    sair(){
        a[0][0]=0,a[0][1]=0;
        a[1][0]=0,a[1][1]=0;
    }
    friend sair operator*(const sair&a,const sair &b){
        sair ans;
        for(int i=0;i<2;i++){
            for(int j=0;j<2;j++){
                for(int k=0;k<2;k++){
                    ans.a[i][j]=(ans.a[i][j]+a.a[i][k]*b.a[k][j]%mod+mod)%mod;
                }
            }
        }
        return ans;
    }
};

sair pow_mul(sair a){
    k-=2;
    sair base;
    base.a[0][0]=1,base.a[0][1]=0;
    base.a[1][0]=0,base.a[1][1]=1;
    while(k){
        if(k&1)
            base=base*a;
        k>>=1;
        a=a*a;
    }
    return base;
}

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    cin>>n>>m>>k;
    sair a;
    a.a[0][0]=(m+mod)%mod,a.a[0][1]=0;
    a.a[1][0]=(n+mod)%mod,a.a[1][1]=0;
    if(k==1) cout<<a.a[1][0]<<endl;
    else if(k==2) cout<<a.a[0][0]<<endl;
    else {
        sair base;
        base.a[0][0]=1,base.a[0][1]=-1;
        base.a[1][0]=1,base.a[1][1]=0;
        sair tmp=pow_mul(base);
        base=tmp*a;
        cout<<(base.a[0][0]+mod)%mod<<endl;
    }

}

 

C

找规律

#include<bits/stdc++.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define sqr(x) ((x)*(x))
#define pb push_back
#define eb emplace_back
#define maxn 100005
#define eps 1e-8
#define pi acos(-1.0)
#define rep(k,i,j) for(int k=i;k<j;k++)
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<long long,int>pli;
typedef pair<int,char> pic;
typedef pair<pair<int,string>,pii> ppp;
typedef unsigned long long ull;
const long long mod=1e9+7;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    ll n,m,k;
    cin>>n>>m>>k;
    ll tmp=(n-1)+(m-1);
    if(n-1==0) tmp=m-1;
    if(m-1==0) tmp=n-1;
    if(n-1==0&&m-1==0) tmp=0;
    if(tmp<k) cout<<-1<<endl;
    else{
        ll ans=0;
        if(k>=n)ans=max(ans,m/(k-n+2));
        if(k>=m)ans=max(ans,n/(k-m+2));
        if(k<n)ans=max(ans,m*(n/(k+1)));
        if(k<m)ans=max(ans,n*(m/(k+1)));
        cout<<ans<<endl;
    }

}

 

D

最短路水题 把要被松弛的边找出来即可

#include<bits/stdc++.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define sqr(x) ((x)*(x))
#define pb push_back
#define eb emplace_back
#define maxn 100005
#define eps 1e-8
#define pi acos(-1.0)
#define rep(k,i,j) for(int k=i;k<j;k++)
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<long long,int>pli;
typedef pair<int,char> pic;
typedef pair<pair<int,string>,pii> ppp;
typedef unsigned long long ull;
const long long mod=1e9+7;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int n,m,k;
vector<pli>ve[200005];
ll dis[200005];
bool book[200005];
bool vis[200005];
int ans;
int co;
void Dijstra(){
    priority_queue<pli,vector<pli>,greater<pli> >Q;
    dis[1]=0;
    int flag;
    Q.push({0,1});
    for(int i=0;i<=n;i++){
        if(book[i]==1){
            Q.push({dis[i],i});
        }
    }
    while(!Q.empty()){
        pli s=Q.top();
        Q.pop();
        int pos=s.second;
        if(!vis[pos]){
            vis[pos]=1;
            for(int i=0;i<ve[pos].size();i++){
                flag=0;
                int u=ve[pos][i].second;
                ll len=ve[pos][i].first;
                if(dis[u]>=dis[pos]+len){
                    if(dis[u]==dis[pos]+len){
                        flag=1;
                    }
                    dis[u]=dis[pos]+len;
                    if(book[u]){
                        ans++;
                        book[u]=0;
                    }
                    if(!flag) Q.push({dis[u],u});
                }
            }
        }
    }
    for(int i=0;i<=n;i++){
        k-=book[i];
    }
    cout<<k<<endl;
}

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    cin>>n>>m>>k;
    int u,v;
    ll c;
    for(int i=0;i<=n;i++){
        dis[i]=0x3f3f3f3f3f3f3f3f;
        vis[i]=0;
        book[i]=0;
    }
    for(int i=1;i<=m;i++){
        cin>>u>>v>>c;
        ve[u].pb({c,v});
        ve[v].pb({c,u});
    }
    for(int i=1;i<=k;i++){
        cin>>u>>c;
        if(dis[u]>c){
            dis[u]=c;
            if(!book[u]){
                book[u]=1;
            }
            else{
                ans++;
            }
        }
        else{
            ans++;
        }
    }
    Dijstra();
    //cout<<ans<<endl;

}

 

E

模拟题+数论

#include<bits/stdc++.h>
using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define sqr(x) ((x)*(x))
#define pb push_back
#define eb emplace_back
#define maxn 100005
#define eps 1e-8
#define pi acos(-1.0)
#define rep(k,i,j) for(int k=i;k<j;k++)
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<long long,int>pli;
typedef pair<int,char> pic;
typedef pair<pair<int,string>,pii> ppp;
typedef unsigned long long ull;
const long long mod=1e9+7;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */
vector<int> a[maxn],ans;
bool book[maxn];

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    int n;
    cin>>n;
    if(n==1){
        cout<<0;
        return 0;
    }
    for(int i=3;i<=n;i++){
        if((i%2==1)&&book[i]==0 ){
            for(int j=i;j<=n;j+=i){
                if(book[j]==0){
                    a[i].push_back(j);
                    book[j]=1;
                }

            }
        }
    }
    for(int i=3;i<=(n/2);i++){
        if(a[i].size()>0){
            if(a[i].size()%2==1){
                a[i].erase(a[i].begin()+1);
                book[2*i]=0;
            }
            while(a[i].size()>0){
                ans.push_back(a[i].back());
                a[i].pop_back();
            }
        }
    }
    for(int i=2 ; i<=n ; i+=2){
        if(book[i]==0){
            a[2].push_back(i);
        }
    }
    for(int i=0;i<a[2].size()-1;i+=2){
        ans.push_back(a[2][i]);
        ans.push_back(a[2][i+1]);
    }
    int answer=(ans.size()>>1);
    cout<<answer<<endl;
    for(int i=ans.size()-1;i>=0;i-=2){
        cout<<ans[i]<<" "<<ans[i-1]<<endl;
    }
}