Solution.cpp

class Solution {
public:
    int countPairs(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        int ans = 0;
        unordered_map<int, int> cnt;

        for (int x : nums) {
            unordered_set<int> vis = {x};
            string s = to_string(x);

            for (int j = 0; j < s.length(); ++j) {
                for (int i = 0; i < j; ++i) {
                    swap(s[i], s[j]);
                    vis.insert(stoi(s));
                    for (int q = i + 1; q < s.length(); ++q) {
                        for (int p = i + 1; p < q; ++p) {
                            swap(s[p], s[q]);
                            vis.insert(stoi(s));
                            swap(s[p], s[q]);
                        }
                    }
                    swap(s[i], s[j]);
                }
            }

            for (int y : vis) {
                ans += cnt[y];
            }
            cnt[x]++;
        }

        return ans;
    }
};