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=;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int a[];

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

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

 void Check(int &x,int &y){
     for(int i=;i<=n;i++){
         for(int j=;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-)/-;
     int u,v;
     for(int i=;i<=nn;i++){
         cin>>u>>v;
         book[u][v]=book[v][u]=;
         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=;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int a[];
 int n;

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

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

         for(int i=;i<co;i++){
             if(b[i-].v>b[i].v&&b[i].v<b[i+].v){
                 cout<<b[i-].pos<<" "<<b[i].pos<<" "<<b[i+].pos<<endl;
                 break;
             }
             if(b[i-].v<b[i].v&&b[i].v>b[i+].v){
                 cout<<b[i-].pos<<" "<<b[i].pos<<" "<<b[i+].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=;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

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

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

 int main(){
     #ifndef ONLINE_JUDGE
       //  freopen("1.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     cin>>n>>m;
     for(int i=;i<=m;i++){
         cin>>s[i]>>t[i];
         if(s[i]>t[i]) swap(s[i],t[i]);
     }
     for(int i=;i<=m;i++){
         for(int j=;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=;i<=m;i++){
         dfs(i,);
     }
     for(int i=;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=;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int prim[]={,,,,,,,,,,,,,,,};
 int n;
 ull ans=-;

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

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