检查集合中的重复项

def remove_duplicates(lst):
    return list(set(lst))

import java.util.HashSet;
import java.util.Set;

public class RemoveDuplicates {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 4, 5, 6, 6};
        Set<Integer> set = new HashSet<Integer>();
        for (int i = 0; i < arr.length; i++) {
            set.add(arr[i]);
        }
        System.out.println(set);
    }
}

function removeDuplicates(arr) {
    return arr.filter((item, index) => {
        return arr.indexOf(item) === index;
    });
}

SELECT column1, column2, COUNT(*)
FROM table_name
GROUP BY column1, column2
HAVING COUNT(*) > 1

#include<iostream>
#include <unordered_set>
#include<vector>

int main() {
    std::vector<int> arr = {1, 2, 3, 4, 4, 5, 6, 6};
    std::unordered_set<int> set(arr.begin(), arr.end());
    std::vector<int> result(set.begin(), set.end());
    return 0;
}