3761. Minimum Absolute Distance Between Mirror Pairs

You are given an integer array nums.

A mirror pair is a pair of indices (i, j) such that:

• 0 <= i < j < nums.length, and
• reverse(nums[i]) == nums[j], where reverse(x) denotes the integer formed by reversing the digits of x. Leading zeros are omitted after reversing, for example reverse(120) = 21.

Return the minimum absolute distance between the indices of any mirror pair. The absolute distance between indices i and j is abs(i - j).

If no mirror pair exists, return -1.

class Solution {
    int rev(int x) {
        string s = to_string(x);
        int res = 0;
        while(s.length()) {
            res = res * 10 + s.back() - '0';
            s.pop_back();
        }
        return res;
    }
public:
    int minMirrorPairDistance(vector<int>& nums) {
        unordered_map<int,int> at;
        int res = INT_MAX;
        for(int i = 0; i < nums.size(); i++) {
            if(at.count(nums[i])) res = min(res, i - at[nums[i]]);
            at[rev(nums[i])] = i;
        }
        return res == INT_MAX ? -1 : res;
    }
};