Crawler Log Folder LeetCode solution in C++

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// 1.using stack
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class Solution {
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 public:
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  int minOperations(vector<string> &logs) {
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    if (logs.size() == 0) return 0;
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    stack<string> st;
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    for (auto x : logs) {
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      if (x[0] != '.') // Move to the child folder so add children
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        st.push(x);
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      else if (x == "../") { // Move to the parent folder of the current folder
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                             // so pop
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        if (!st.empty())
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          st.pop();
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        else
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          continue; // don’t move the pointer beyond the main folder.
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      }
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    }
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    return st.size();
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  }
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};
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// 2.
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class Solution {
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 public:
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  int minOperations(vector<string> &logs) {
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    int ans = 0;
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    for (string log : logs) {
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      if (log == "../") { // go deeper
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        ans--;
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        ans = max(ans, 0);
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      } else if (log != "./") // one level up
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        ans++;
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    }
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    return ans;
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  }
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};
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// 3.
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class Solution {
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 public:
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  int minOperations(vector<string> &logs) {
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    int res = 0;
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    for (string s : logs) {
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      if (s == "../")
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        res = max(0, --res);
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      else if (s == "./")
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        continue;
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      else
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        res++;
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    }
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    return res;
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  }
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};