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[105];
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=0,s=0;
    int posd,poss;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        if(a[i]%2) 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[105];
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=0;
    while(n){
        if(n>3){
            n-=2;
            cout<<str[co]<<str[co+1]<<'-';
            co+=2;
        }
        else{
            if(n==3)
                cout<<str[co]<<str[co+1]<<str[co+2]<<endl;
            else
                cout<<str[co]<<str[co+1]<<endl;
            n=0;
        }
    }
}

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[305][305];

int main(){
    #ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
    #endif
    //std::ios::sync_with_stdio(false);
    int n;
    cin>>n;
    for(int i=0;i<n;i++){
        for(int j=0;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=0;
        for(int i=0;i<n;i++){
            for(int j=0;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/2<<" ";
    }
}

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[1005];

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=0;i<=1001;i++) fa[i]=i;
    for(int i=1;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=0;i<ve.size();i++){
        u=ve[i].first;
        for(int j=1;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=0;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=257;
/*#ifndef ONLINE_JUDGE
        freopen("1.txt","r",stdin);
#endif */
int Check(string s1,string s2){
    int len=0;
    if(s1.find(s2)!=-1) return s1.length();
    if(s2.find(s1)!=-1) return s2.length();
    int len1=s1.length();
    int len2=s2.length();
    int ans=len1+len2;
    int i=len1-1,j=0;
    ull aa=0,bb=0;
    ull flag=1;
   // cout<<s1<<" "<<s2<<endl;
    while(i>=0&&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+1;
        }
        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;
}