Codeforces Beta Round #25 (Div. 2 Only)

Codeforces Beta Round #25 (Div. 2 Only)

http://codeforces.com/contest/25

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 500005
 typedef long long ll;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int n;
 int a[];
 map<int,int>mp;

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

 }

B

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 500005
 typedef long long ll;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int n;
 int a[];
 map<int,int>mp;

 int main(){
     #ifndef ONLINE_JUDGE
   //      freopen("1.txt","r",stdin);
     #endif
     std::ios::sync_with_stdio(false);
     int n;
     cin>>n;
     string str;
     cin>>str;
     int co=;
     while(n){
         if(n>){
             n-=;
             cout<<str[co]<<str[co+]<<'-';
             co+=;
         }
         else{
             if(n==)
                 cout<<str[co]<<str[co+]<<str[co+]<<endl;
             else
                 cout<<str[co]<<str[co+]<<endl;
             n=;
         }
     }
 }

C

用floyd跑，类似DP的思想

 #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 500005
 typedef long long ll;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 ll dp[][];

 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++){
         for(int j=;j<n;j++){
             cin>>dp[i][j];
         }
     }
     int m;
     cin>>m;
     ll u,v,c;
     while(m--){
         cin>>u>>v>>c;
         u--,v--;
         ll ans=;
         for(int i=;i<n;i++){
             for(int j=;j<n;j++){
                 dp[i][j]=min(dp[i][j],min(dp[i][u]+c+dp[v][j],dp[i][v]+c+dp[u][j]));
                 ans+=dp[i][j];
             }
         }
         cout<<ans/<<" ";
     }
 }

D

并查集，判断是否成环，成环的话把可以构成环的边删去并找到另一个集合把他们连起来

 #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 500005
 typedef long long ll;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */

 int fa[];

 int Find(int x){
     int r=x,y;
     while(x!=fa[x]){
         x=fa[x];
     }
     while(r!=x){
         y=fa[r];
         fa[r]=x;
         r=y;
     }
     return x;
 }

 bool join(int x,int y){
     int xx=Find(x);
     int yy=Find(y);
     if(xx!=yy){
         fa[xx]=yy;
         return true;
     }
     return false;
 }

 int main(){
     #ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
     #endif
     //std::ios::sync_with_stdio(false);
     int n;
     cin>>n;
     int u,v;
     vector<pair<int,int> >ve;
     for(int i=;i<=;i++) fa[i]=i;
     for(int i=;i<n;i++){
         cin>>u>>v;
         if(!join(u,v)) ve.push_back(make_pair(u,v));
     }
     vector<pair<pair<int,int>,pair<int,int> > >ans;
     for(int i=;i<ve.size();i++){
         u=ve[i].first;
         for(int j=;j<=n;j++){
             if(join(u,j)){
                 ans.push_back(make_pair(make_pair(u,ve[i].second),make_pair(u,j)));
                 break;
             }
         }
     }
     cout<<ans.size()<<endl;
     for(int i=;i<ans.size();i++){
         cout<<ans[i].first.first<<" "<<ans[i].first.second<<" "<<ans[i].second.first<<" "<<ans[i].second.second<<endl;
     }
 }

E

字符串hash 找到一个前缀和另一个后缀最长相同的长度，也可以用kmp做

 #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 500005
 typedef long long ll;
 typedef unsigned long long ull;
 const ull MOD=;
 /*#ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
 #endif */
 int Check(string s1,string s2){
     int len=;
     if(s1.find(s2)!=-) return s1.length();
     if(s2.find(s1)!=-) return s2.length();
     int len1=s1.length();
     int len2=s2.length();
     int ans=len1+len2;
     int i=len1-,j=;
     ull aa=,bb=;
     ull flag=;
    // cout<<s1<<" "<<s2<<endl;
     while(i>=&&j<len2){
         aa=s1[i]*flag+aa;
         flag=flag*MOD;
         bb=bb*MOD+s2[j];
        // cout<<s1[i]<<" "<<s2[j]<<" "<<aa<<" "<<bb<<endl;
         if(aa==bb){
             len=j+;
         }
         i--,j++;
     }
     return ans-len;
 }

 int main(){
     #ifndef ONLINE_JUDGE
         freopen("1.txt","r",stdin);
     #endif
     //std::ios::sync_with_stdio(false);
     string s1,s2,s3;
     cin>>s1>>s2>>s3;
     int len1=s1.length(),len2=s2.length(),len3=s3.length();
    // cout<<len1<<" "<<len2<<" "<<len3<<" "<<len1+len2+len3<<endl;
     int ans=0x3f3f3f3f;
     ans=min(ans,(Check(s1,s2)+Check(s2,s3)-len2));
     ans=min(ans,Check(s1,s3)+Check(s3,s2)-len3);
     ans=min(ans,Check(s2,s1)+Check(s1,s3)-len1);
     ans=min(ans,Check(s2,s3)+Check(s3,s1)-len3);
     ans=min(ans,Check(s3,s1)+Check(s1,s2)-len1);
     ans=min(ans,Check(s3,s2)+Check(s2,s1)-len2);
     cout<<ans<<endl;
 }