Smallest Positive Missing Number in an Unsorted Array Code

spmn.cpp

 int findMissing(int arr[], int n) { 
        for(int i = 0; i < n; i++){
          //looking for all the conditions
            while(arr[i] >= 1 && arr[i] <= n && arr[i] != arr[arr[i]-1])
                swap(arr[i], arr[arr[i]-1]);
        }
   //to check our missing number. For explaination, refer the article.
        for(int i = 0; i < n; i++){
            if(arr[i] != i + 1)
                return i + 1;
        }
    // if array has all the values from 1 to n
    return n + 1;
    }