B. Binary Period（水、Educational Codeforces Round 86 (Rated for Div. 2)）

B. Binary Period

CF 1342B

Meaning: given string $t$ , the output string$s$（$|S|$ length less$2\cdot |t|$ ), such thatssThe period in$s$ is the smallest.

Idea: Judge ttWhether there are0, 1 0, 1 in$t$ at the same time$0、1$

• If single, the minimum period is $1$ : Direct output
• If there are 0, 1 0, 1 at the same time$0,1$ , the minimum period is$2$ : Output$01$ interval string

int n;
int main(){
    
    
    int t,tt,f1=0,f0=0,len;
    LL x,a,b,y,ans;
    cin>>t;
    string s;
    while(t--){
    
    
        cin>>s;
        f1=0;f0=0;
        len=s.length();
        for(int i=0;i<len;i++){
    
    
            if(s[i]-'0')f1++;
            else f0++;
        }
        if(f1==0){
    
    
            for(int i=1;i<=len;i++)
                cout<<"0";
            cout<<endl;
            continue;
        }
        if(f0==0){
    
    
            for(int i=1;i<=len;i++)
                cout<<"1";
            cout<<endl;
            continue;
        }
        if(s[0]=='0'){
    
    
            for(int i=0;i<len;i++){
    
    
                cout<<"01";
            }
            cout<<endl;
            continue;
        }
        if(s[0]=='1'){
    
    
            for(int i=0;i<len;i++){
    
    
                cout<<"10";
            }
            cout<<endl;
            continue;
        }
    }
}