https://practice.geeksforgeeks.org/problems/union-of-two-arrays/0

## Union

Does not handle duplicates

``````class Solution {
public:
int doUnion(int a[], int n, int b[], int m) {
int i = 0, j = 0;
sort(a, a + n);
sort(b, b + m);
vector<int> v;
while (i < n && j < m) {
if (a[i] < b[j]) {
v.push_back(a[i]);
i++;
} else if (a[i] > b[j]) {
v.push_back(b[j]);
j++;
} else {
v.push_back(a[i]);
// or
// v.push_back(b[j]);
i++;
j++;
}
}

while (i < n)
v.push_back(a[i++]);

while (j < m)
v.push_back(b[j++]);

return v.size();
}
};
``````

Handles duplicates

``````class Solution{
public:
int doUnion(int a[], int n, int b[], int m)  {
set<int> st;
for (int i = 0; i < n; i++) {
st.insert(a[i]);
}

for (int i = 0; i < m; i++) {
st.insert(b[i]);
}

return st.size();
}
};
``````

## Intersection

https://leetcode.com/problems/intersection-of-two-arrays/

``````class Solution {
public:
vector<int> intersection(vector<int> &nums1, vector<int> &nums2) {
int i = 0, j = 0;
int n = nums1.size(), m = nums2.size();
sort(nums1.begin(), nums1.end());
sort(nums2.begin(), nums2.end());

set<int> st;
while (i < n && j < m) {
if (nums1[i] < nums2[j]) {
i++;
} else if (nums1[i] > nums2[j]) {
j++;
} else {
st.insert(nums1[i]);
// or
// v.push_back(b[j]);
i++;
j++;
}
}
return vector<int>(st.begin(), st.end());
}
};
``````