Codeforces Round 785 (Div. 2)

A - Subtle Substring Subtraction

/*
 *                                                     __----~~~~~~~~~~~------___
 *                                    .  .   ~~//====......          __--~ ~~
 *                    -.            \_|//     |||\\  ~~~~~~::::... /~
 *                 ___-==_       _-~o~  \/    |||  \\            _/~~-
 *         __---~~~.==~||\=_    -_--~/_-~|-   |\\   \\        _/~
 *     _-~~     .=~    |  \\-_    '-~7  /-   /  ||    \      /
 *   .~       .~       |   \\ -_    /  /-   /   ||      \   /
 *  /  ____  /         |     \\ ~-_/  /|- _/   .||       \ /
 *  |~~    ~~|--~~~~--_ \     ~==-/   | \~--===~~        .\
 *           '         ~-|      /|    |-~\~~       __--~~
 *                       |-~~-_/ |    |   ~\_   _-~            /\
 *                            /  \     \__   \/~                \__
 *                        _--~ _/ | .-~~____--~-/                  ~~==.
 *                       ((->/~   '.|||' -_|    ~~-/ ,              . _||
 *                                  -_     ~\      ~~---l__i__i__i--~~_/
 *                                  _-~-__   ~)  \--______________--~~
 *                                //.-~~~-~_--~- |-------~~~~~~~~
 *                                       //.-~~~--\
 *                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *                               神兽保佑            永无BUG
 */
 #include<bits/stdc++.h>
 #define int long long
 using namespace std;
 void solve()
 {
     string s; 
     cin>>s;
     int len=s.size();
     int suma=0,sumb=0;
     for(int i=0;i<s.size();i++) suma+=(s[i]-'a'+1);
    if(s.size()%2==0) return cout<<"Alice "<<suma<<endl,void();
     sumb=min(s[len-1]-'a'+1,s[0]-'a'+1);
//     cout<<suma<<' '<<sumb<<endl;
     suma-=sumb;
     if(sumb>suma) return cout<<"Bob "<<sumb-suma<<endl,void();
     else return cout<<"Alice "<<suma-sumb<<endl,void();
 }
 signed main()
 {
    int t; cin>>t; while(t--) solve();
     return 0;
 }

B - A Perfectly Balanced String?

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
void solve()
{
    string s; cin>>s;
    bool f1=false,f2=false;
    int len=s.size(),num=0;
    map<char,int>mp;
    for(int i=0;i<len;i++){
        if(s[i]!=s[0]) f1=true;
        if(mp[s[i]]==0) num++;
        mp[s[i]]++;
        if(mp[s[i]]>=2) f2=true;
    }
    if(!f1||!f2) return cout<<"Yes"<<endl,void();
    mp.clear();
    for(int i=num;i<len;i++)
        if(s[i]!=s[i-num]) return cout<<"No"<<endl,void();
    cout<<"Yes"<<endl;
}
int main()
{
    int t; cin>>t;
    while(t--){
        solve();
    }
}

//第二种:

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10;
string s;
int n,m;
bool check(char x,char y)
{
    int cur=0;
    for(auto c:s){
        if(c==x) cur--,cur=(cur<0)?0:cur;
        if(c==y) cur++;
        if(cur>1) return false;
    }
    return true;
}
void solve()
{
    cin>>s;
    map<char,int>mp;
    for(auto c:s) mp[c]++;
    for(char i='a';i<='z';i++){
        if(!mp[i]) continue;
        for(char j='a';j<='z';j++){
            if(!mp[j]||i==j) continue;
            if(!check(i,j)) return cout<<"No"<<endl,void();
        }
    }
    cout<<"Yes"<<endl;
}
int main()
{
    int t;cin>>t;while(t--) solve();
}

C - Palindrome Basis

#include<bits/stdc++.h>
#define int long long 
using namespace std;
const int N=5e4+10,mod=1e9+7;
bool vis[N];
int dp[N];
bool check(int x)
{
    string s=to_string(x);
    for(int i=0,j=s.size()-1;i<j;i++,j--)
        if(s[i]!=s[j]) return false;
    return true;
}
void solve()
{
    int n; cin>>n;
    cout<<dp[n]<<endl;
}
signed main()
{
    for(int i=1;i<=50000;i++) 
        if(check(i)) vis[i]=true;
    vector<int>w;
    w.push_back(-1);
    for(int i=1;i<=50000;i++) 
        if(vis[i]) w.push_back(i);
    dp[0]=1;
    for(int i=1;i<=w.size()-1;i++)
        for(int j=w[i];j<=50000;j++)
            dp[j]=(dp[j-w[i]]+dp[j])%mod;
    int t; cin>>t; while(t--) solve();
    return 0;
}