c++(4 ms) THE FASTEST, simple, easy & small solution 
IntuitionApproachComplexity
Time complexity:

Space complexity:
Code
# Intuition
<!-- Describe your first thoughts on how to solve this problem. -->

# Approach
<!-- Describe your approach to solving the problem. -->

# Complexity
- Time complexity:
<!-- Add your time complexity here, e.g. $$O(n)$$ -->

- Space complexity:
<!-- Add your space complexity here, e.g. $$O(n)$$ -->

# Code
```cpp []
class Solution {
public:
  int similarPairs(vector<string>& words) {
    int ans = 0;
    unordered_map<int, int> mp;

    for(auto &w: words){
      int mask = 0;
      for(char c: w) mask |= 1<<(c-'a');
      ans += mp[mask]++;
    }      

    return ans;
  }
};
```
['C++']