Time:O(n) Space:O(1) C++ class Solution { public: int minOperations(vector<string>& logs) { int ans = 0; for (const string& log : logs) { if (log == "./") continue; if (log == "../") ans = max(0, ans - 1); else ++ans; } return ans; } }; JAVA class Solution { public int minOperations(String[] logs) { int ans = 0; for (final String log : logs) { if (log.equals("./")) continue; if (log.equals("../")) ans = Math.max(0, ans - 1); else ++ans; } return ans; } }