Use a loop structure like a for statement to check if all conditions are satisfied.

Check if it contains an uppercase letter by inspecting all characters in a total of \(\mathrm{O}(|S|)\) time.

Similarly, check if it contains an lowercase letter by inspecting all characters in a total of \(\mathrm{O}(|S|)\) time.

Check if \(S_i \neq S_j\) for every pair of integers \((i, j)\) such that \(1 \le i < j \le |S|\) in a total of \(\mathrm{O}(|S|^2)\) time.

In C++, one can check if a character is an uppercase English letter by ‘A’ <= s[i] && s[i] <= ‘Z’ or by isupper function.

#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  cin >> s;
  bool big = false,small = false;
  for(int i = 0; i < s.size(); i++){
    if(isupper(s[i])) big = true;
    else small = true;
  }
  bool diff = true;
  for(int i = 0; i < s.size(); i++){
    for(int j = i + 1; j < s.size(); j++){
      if(s[i] == s[j]) diff = false;
    }
  }
  if(big && small && diff) cout << "Yes" << endl;
  else cout << "No" << endl;
}