Intersection of Two Arrays II

leetcode, easy

Problem Statement #

Given a linked list of N nodes such that it may contain a loop. A loop here means that the last node of the link list is connected to the node at position X. If the link list does not have any loop, X=0. Remove the loop from the linked list, if it is present.

Appris #

Streams in Java take much time then simple array value insertion. arr1 method took 14ms, where as arr2 method only took 6ms

int[] arr1 = lst.stream().mapToInt(Integer::intValue).toArray();

int arr2[] = new int[lst.size()];
for(int i=0;i<lst.size();i++) {
    arr2[i] = lst.get(i);
}

Solution #

class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {

        // Map to count frequeny of numbers
        Map<Integer,Integer> map = new HashMap<>();
        
        for(int i:nums1){
            map.put(i,map.getOrDefault(i,0)+1);
        }
        
        // Use Resizeable array, since there may n or m numbers 
        // of numbers in results 
        ArrayList<Integer> lst = new ArrayList<>();
        
        for(int i:nums2){
            // for each number in array 2, update the character 
            // frequency of initial map 
            if(map.containsKey(i)==true && map.get(i)>0){
                lst.add(i);
                map.put(i,map.get(i)-1);
            }
        }
        
        // ArrayList -> Array 
        int arr[] = new int[lst.size()];
        for(int i=0;i<lst.size();i++) {
            arr[i] = lst.get(i);
        }

        return arr;
    }
}