1539.kth missing positive number

class Solution {
    public int findKthPositive(int[] arr, int k) {
        if(arr[arr.length-1]==arr.length){
            return arr[arr.length-1]+k;
        }
        int ans=binary(arr,k);
        if(ans==-1){
            int value=arr[arr.length-1]-(arr.length);
            int find=k-value;
           return arr[arr.length-1]+find;
        }
        int c=0;
        int a=arr[ans]-1;
        int index=ans-1;  
      int val=arr[ans]-(ans+1);
      int val2=arr[ans]-1;
        while(true){
            if(index>=0){
            if(val2==arr[index]){
                val2--;
                index--;
              continue;
            }
            }
            if(val==k){
                return val2;
            }
             val--;
            val2--;
        }
    }
    static int binary(int arr[],int k){
        int l=0;
        int r=arr.length-1;
        int si=-1;
        while(l<=r){
            int mid=l+(r-l)/2;
            int mid2=arr[mid]-(mid+1);
           
           if(mid2<k){
              l=mid+1;
            }
             else{
               si=mid; 
               r=mid-1;
            }
        }
        return si;
    }
}