Describe the Painting LeetCode solution in C++

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class Solution {
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 public:
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  vector<vector<long long>> splitPainting(vector<vector<int>> &seg) {
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    vector<vector<long long>> v;
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    map<long long, long long> m;
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    long long int i = 0;
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    while (i < seg.size()) {
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      m[seg[i][0]] += seg[i][2];
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      m[seg[i][1]] -= seg[i][2];
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      i++;
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    }
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    long long int j = 0, k = 0;
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    for (auto x : m) {
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      long long int prev = j;
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      j += x.second;
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      if (prev > 0) v.push_back({k, x.first, prev});
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      k = x.first;
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    }
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    return v;
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  }
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};