https://codeforces.com/problemset/problem/1384/A

help
1

int n;
cin >> n;

    string s(200, 'a');
    cout << s << endl;

    for (int i = 0; i < n; ++i){
        int u;
        cin >> u;
        s[u] = s[u] == 'a' ? 'b' : 'a';
        cout << s << endl;
    }

can anyone explain
s[u] = s[u] == ‘a’ ? ‘b’ : ‘a’;
this part of the code

2

Have you read about ternary if else ?

if(s[u]=='a')
s[u]='b';
else
s[u]='a';