Leetcode Find the Duplicate Number problem solution

In this Leetcode Find the Duplicate Number problem solution we have given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

There is only one repeated number in nums, return this repeated number. You must solve the problem without modifying the array nums and uses only constant extra space.

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Problem solution in Python.

d = dict(collections.Counter(nums))
        print(d)
        for k in d:
            if d[k] > 1:
                return k

Problem solution in Java.

if(nums == null || nums.length == 0) {
            return 0;
        }
        int l = 1, r = nums.length;
        while(l < r){
            int cnt = 0;
            int mid = l + (r-l)/2;
            for(int num : nums) {
                if(num <= mid) cnt++;
            }
            if(cnt <= mid) {
                l = mid+1;
            } else {
                r = mid;
            }
        }
        return l;

Problem solution in C++.

class Solution {
public:
    int findDuplicate(vector<int>& nums) {
        
        vector<int> map(nums.size(), 0 );
        
        for(int i = 0; i < nums.size(); i++)
        {
            if(++map[nums[i]] > 1)
                return nums[i];
        }
        return 0;
    }
};

Problem solution in C.

int findDuplicate(int* a, int numsSize) {

int i=0;

while(i<numsSize)
{
    while(a[i] != (i+1))
    {
        if(a[a[i]-1] == a[i])
            return a[i];
        else
        {
            //swap a[a[i]-1] and a[i]
            a[a[i]-1] = a[i] + a[a[i]-1] - (a[i] = a[a[i]-1]);
        }
    }
    i++;
}
}

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