1539_Kth_Missing_Positive_Number

Leetcode 1539: Kth Missing Positive Number
Detailed video explanation: 
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C++:
----
class Solution {
public:
    int findKthPositive(vector<int>& arr, int k) {
        int next_int = 1;
        for(int a: arr){
            if(a == next_int)
                next_int++;
            else{
                int gap = a - next_int;
                if(gap >= k) return next_int + k -1;
                k -= gap;
                next_int = a+1;
            }
        }
        return next_int + k -1;
    }
};



Java:
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class Solution {
    public int findKthPositive(int[] arr, int k) {
        int next_int = 1;
        for(int a: arr){
            if(a == next_int)
                next_int++;
            else{
                int gap = a - next_int;
                if(gap >= k) return next_int + k -1;
                k -= gap;
                next_int = a+1;
            }
        }
        return next_int + k -1;
    }
}




Python3:
--------
class Solution:
    def findKthPositive(self, arr: List[int], k: int) -> int:
        next_int = 1
        for a in arr:
            if a == next_int:
                next_int += 1
            else:
                gap = a - next_int
                if gap >= k: return next_int + k -1
                k -= gap
                next_int = a+1
        return next_int + k -1