Find All Duplicates in an Array

class Solution {
public:
    vector<int> findDuplicates(vector<int>& nums) {
        vector<int> ans;
        for (int v : nums) {
            int i = abs(v) - 1;
            if (nums[i] < 0) ans.push_back(i + 1);
            else nums[i] = -nums[i];
        }
        return ans;
    }
};

func findDuplicates(nums []int) []int {
    ans := []int{}
    for _, v := range nums {
        i := v
        if i < 0 {
            i = -i
        }
        i--
        if nums[i] < 0 {
            ans = append(ans, i+1)
        } else {
            nums[i] = -nums[i]
        }
    }
    return ans
}

from typing import List

class Solution:
    def findDuplicates(self, nums: List[int]) -> List[int]:
        ans: List[int] = []
        for v in nums:
            i = abs(v) - 1
            if nums[i] < 0:
                ans.append(i + 1)
            else:
                nums[i] = -nums[i]
        return ans

function findDuplicates(nums) {
    const ans = [];
    for (const v of nums) {
        const i = Math.abs(v) - 1;
        if (nums[i] < 0) ans.push(i + 1);
        else nums[i] = -nums[i];
    }
    return ans;
}

class Solution {
    public List<Integer> findDuplicates(int[] nums) {
        List<Integer> ans = new ArrayList<>();
        for (int v : nums) {
            int i = Math.abs(v) - 1;
            if (nums[i] < 0) ans.add(i + 1);
            else nums[i] = -nums[i];
        }
        return ans;
    }
}

function findDuplicates(nums: number[]): number[] {
    const ans: number[] = [];
    for (const v of nums) {
        const i = Math.abs(v) - 1;
        if (nums[i] < 0) ans.push(i + 1);
        else nums[i] = -nums[i];
    }
    return ans;
}