LeetCode Problem
350. Intersection of Two Arrays II
Link to LeetCode
Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must appear as many times as it shows in both arrays and you may return the result in any order.
note : The intersection of two arrays is defined as the set of elements that are present in both arrays.
Example 1:
Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]
Example 2:
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]
Explanation: [9,4] is also accepted.
public int[] intersect(int[] nums1, int[] nums2) {
HashMap< Integer, Integer> map = new HashMap< Integer, Integer>();
for(int i: nums1){
if(map.containsKey(i)){
map.put(i, map.get(i)+1);
}else{
map.put(i, 1);
}
}
ArrayList< Integer> list = new ArrayList< Integer>();
for(int i: nums2){
if(map.containsKey(i)){
if(map.get(i)>1){
map.put(i, map.get(i)-1);
}else{
map.remove(i);
}
list.add(i);
}
}
int[] result = new int[list.size()];
int i =0;
while(i< list.size()){
result[i]=list.get(i);
i++;
}
return result;
}
// If the arrays are sorted, then we can use two points.
public int[] intersect(int[] nums1, int[] nums2) {
Arrays.sort(nums1);
Arrays.sort(nums2);
ArrayList< Integer> list = new ArrayList< Integer>();
int p1=0, p2=0;
while(p1< nums1.length && p2< nums2.length){
if(nums1[p1]< nums2[p2]){
p1++;
}else if(nums1[p1]>nums2[p2]){
p2++;
}else{
list.add(nums1[p1]);
p1++;
p2++;
}
}
int[] result = new int[list.size()];
int i=0;
while(i< list.size()){
result[i]=list.get(i);
i++;
}
return result;
}