A good way into this one is to ask: what do we need to remember so we never redo work blindly? For 1598. Crawler Log Folder, the solution in this repository is mainly a stack solution.
Guide
What?
The first job is to translate the English prompt into state, transition, and stopping conditions. Instead of trying to be clever immediately, read the code as a sequence of questions:
- What state are we keeping?
- How do we move from one state to the next?
- When do we know the answer is already determined?
For this file, the main tools are: stack.
The notes already sitting in the source point us in the right direction:
- stack
Guide
When?
This pattern shows up when the brute force version has too many repeated checks, too many possible branches, or too much bookkeeping to do by hand. The accepted code reduces that pressure by storing exactly the information that remains useful later.
The important function names to track are minOperations.
Guide
Why?
The win comes from making each line carry responsibility: store the useful state, discard the rest, keep moving.
- The stack stores unfinished context, which is usually the cleanest way to handle nested or monotonic structure.
- The final return is not magic; it is the invariant after the loops or recursion have finished doing their accounting.
Guide
How?
Walk through the solution in this order:
- Read the setup variables first.
- Follow the main loop or recursive helper next.
- Watch where invalid states get skipped.
- Check which value survives to the return statement.
The most important competitive-programming habit here is to trust the invariant. Once the invariant is right, the loops become much less scary.
Guide
Complexity
- Time: O(n) to O(n log n), depending on the dominant loop or data structure operation
- Space: O(n) in the usual case for auxiliary containers or recursion
Guide
C++ Solution
Your submission
The accepted solution
01//stack
02//Runtime: 8 ms, faster than 91.48% of C++ online submissions for Crawler Log Folder.
03//Memory Usage: 11.2 MB, less than 5.03% of C++ online submissions for Crawler Log Folder.
04class Solution {
05public:
06 int minOperations(vector<string>& logs) {
07 stack<string> stk;
08
09 for(const string& log : logs){
10 if(log == "./"){
11
12 }else if(log == "../"){
13 if(!stk.empty()) stk.pop();
14 }else{
15 stk.push(log);
16 }
17 }
18
19 return stk.size();
20 }
21};Cost