Codeforces Beta Round #27 (Codeforces format, Div. 2)

Codeforces Beta Round #27 (Codeforces format, Div. 2)

http://codeforces.com/contest/27

A

#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 maxn 1000005
typedef long long ll;
typedef unsigned long long ull;
const ull MOD=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int a[3005];

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    std::ios::sync_with_stdio(false);
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    sort(a+1,a+n+1);
    int i;
    for(i=1;i<=n;i++){
        if(a[i]!=i){
            cout<<i<<endl;
            break;
        }
    }
    if(i==n+1) cout<<n+1<<endl;
}

B

找出度数大的那个点

#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 maxn 1000005
typedef long long ll;
typedef unsigned long long ull;
const ull MOD=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int book[55][55];
int n;
int d[55];

void Check(int &x,int &y){
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(i==j) continue;
            if(!book[i][j]){
                x=i,y=j;
                return;
            }
        }
    }
}

int main(){
    #ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
    #endif
    std::ios::sync_with_stdio(false);
    cin>>n;
    int nn=n*(n-1)/2-1;
    int u,v;
    for(int i=1;i<=nn;i++){
        cin>>u>>v;
        book[u][v]=book[v][u]=1;
        d[u]++;
    }
    int x,y;
    Check(x,y);
    if(d[x]>d[y]){
        cout<<x<<" "<<y<<endl;
    }
    else{
        cout<<y<<" "<<x<<endl;
    }
}

C

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 maxn 1000005
typedef long long ll;
typedef unsigned long long ull;
const ull MOD=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int a[100005];
int n;

int Check(){
    int flag=0;
    for(int i=1;i<n;i++){///<<<<<<
        if(a[i]>a[i+1]){
            flag=1;
        }
    }
    if(flag==0){
        return 1;
    }
    flag=0;
    for(int i=1;i<n;i++){///>>>>>>
        if(a[i]<a[i+1]){
            flag=2;
        }
    }
    if(flag==0) return 2;
    return -1;
}

struct sair{
    int v,pos;
}b[100005];
int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    std::ios::sync_with_stdio(false);
    cin>>n;
    int co=1;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        if(a[i]!=a[i-1]){
            b[co].v=a[i];
            b[co].pos=i;
            co++;
        }
    }
    co--;
    int flag=Check();
    if(flag==1||flag==2){
        cout<<0<<endl;
    }
    else{
        cout<<3<<endl;

        for(int i=2;i<co;i++){
            if(b[i-1].v>b[i].v&&b[i].v<b[i+1].v){
                cout<<b[i-1].pos<<" "<<b[i].pos<<" "<<b[i+1].pos<<endl;
                break;
            }
            if(b[i-1].v<b[i].v&&b[i].v>b[i+1].v){
                cout<<b[i-1].pos<<" "<<b[i].pos<<" "<<b[i+1].pos<<endl;
                break;
            }
        }
    }
}

D

用类似二分染色的思想，把交叉的道路染成不同的颜色，如果判断的时候出现交叉的道路有相同的颜色，就输出Impossible

#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 maxn 1000005
typedef long long ll;
typedef unsigned long long ull;
const ull MOD=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

vector<int>ve[105];
int n,m;
int s[105],t[105];
int vis[105];
int col[105];

void dfs(int pos,int c){
    if(vis[pos]) return;
    vis[pos]=1;
    col[pos]=c;
    for(int i=0;i<ve[pos].size();i++){
        dfs(ve[pos][i],c^1);
        if(col[pos]==col[ve[pos][i]]){
            cout<<"Impossible"<<endl;
            exit(0);
        }
    }
}

int main(){
    #ifndef ONLINE_JUDGE
      //  freopen("1.txt","r",stdin);
    #endif
    std::ios::sync_with_stdio(false);
    cin>>n>>m;
    for(int i=1;i<=m;i++){
        cin>>s[i]>>t[i];
        if(s[i]>t[i]) swap(s[i],t[i]);
    }
    for(int i=1;i<=m;i++){
        for(int j=1;j<=m;j++){
            if(s[i]<s[j]&&t[i]<t[j]&&s[j]<t[i]){
                ve[i].pb(j);
                ve[j].pb(i);
            }
        }
    }
    for(int i=1;i<=m;i++){
        dfs(i,0);
    }
    for(int i=1;i<=m;i++){
        if(col[i]) cout<<'i';
        else cout<<'o';
    }
}

E

知识点：反素数

参考博客：https://www.cnblogs.com/handsomecui/p/5017484.html

#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 maxn 1000005
typedef long long ll;
typedef unsigned long long ull;
const ull MOD=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */

int prim[16]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53};
int n;
ull ans=-1;

void dfs(int pos,ull v,int num){
    if(num==n&&ans>v) ans=v;
    for(int i=1;i<=63;i++){
        if(num*(i+1)>n||v*prim[pos]>ans) break;
        v*=prim[pos];
        dfs(pos+1,v,num*(i+1));
    }
}

int main(){
    #ifndef ONLINE_JUDGE
     //   freopen("1.txt","r",stdin);
    #endif
    std::ios::sync_with_stdio(false);
    cin>>n;
    dfs(0,1,1);
    cout<<ans<<endl;
}