Check if One String Swap Can Make Strings Equal LeetCode solution in C++

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/*
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    https://leetcode.com/problems/check-if-one-string-swap-can-make-strings-equal/
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    Find the number of positions which are different.
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    Now the strings can be made equal only if there are 0
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    different positions or 2 different positions and there are
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    chars on those positions which when swaped will make the
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    strings equal.
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    TC: O(N)
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    SC: O(1), At most 2 values are put in the diff_pos vector
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*/
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class Solution {
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 public:
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  bool areAlmostEqual(string s1, string s2) {
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    // find the number of diff positions
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    vector<int> diff_pos;
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    for (int i = 0; i < s1.size(); i++) {
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      if (s1[i] != s2[i]) diff_pos.emplace_back(i);
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      // If there are more than 2 char positions that differ,
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      // the single swap op cannot anyway make the two strings equal
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      if (diff_pos.size() > 2) return false;
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    }
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    // when the chars are exactly the same
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    if (diff_pos.empty()) return true;
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    // only one pair of diff positions, check if swapping makes them equal
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    if (diff_pos.size() == 2) swap(s1[diff_pos[0]], s1[diff_pos[1]]);
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    return s1 == s2;
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  }
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};