To find the minimum difference between any pair of elements in the array, the most striaght forward approach is to generate all possible pairs and check if their difference is minimum.

Considering each element as the first element of a pair, run a loop to get second element of pair and find their difference.
If the difference is smaller than minimum difference found so far then update the minimum distance.
Return the minimum difference once all the pairs are checked.

Code

#include <bits/stdc++.h>
using namespace std;

// Class containing the brute-force method
class Solution {
public:
    // Function to find minimum absolute difference
    int minimumDifference(vector<int>& arr) {
        int n = arr.size();
        int minDiff = INT_MAX;

        // Loop through each pair
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {

                // Calculate absolute difference
                int diff = abs(arr[i] - arr[j]);

                // Update minDiff if smaller
                if (diff < minDiff)
                    minDiff = diff;
            }
        }

        // Return the minimum difference
        return minDiff;
    }
};

// Main function
int main() {
    vector<int> arr = {4, 9, 1, 32, 13};

    // Create object
    Solution sol;

    // Call the function
    int result = sol.minimumDifference(arr);

    // Print the result
    cout << "Minimum difference is " << result << endl;

    return 0;
}