intersection-of-two-array-easy.cpp

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        sort(nums1.begin(), nums1.end());
        sort(nums2.begin(), nums2.end());
        
        int i1 = 0, i2 = 0;
        vector<int> result;
        while (i1 < nums1.size() && i2 < nums2.size()) {
            if (nums1[i1] == nums2[i2]) {
                if (result.empty() || nums1[i1] != result.back()) {
                    result.push_back(nums1[i1]);                    
                }
                i1++;
                i2++;
            } else if (nums1[i1] < nums2[i2]) {
                i1++;
            } else {
                i2++;
            }
        }
        return result;
    }
};

intersection-of-two-array-fast.cpp

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        sort(nums1.begin(), nums1.end());
        sort(nums2.begin(), nums2.end());
        
        int i1 = 0, i2 = 0;
        vector<int> result;
        while (i1 < nums1.size() && i2 < nums2.size()) {
            if (nums1[i1] == nums2[i2]) {
                result.push_back(nums1[i1]);                
                while (i1 < nums1.size() && nums1[i1] == result.back()) {
                    i1++;
                }
                while (i2 < nums2.size() && nums2[i2] == result.back()) {
                    i2++;
                }
            } else if (nums1[i1] < nums2[i2]) {
                i1++;
            } else {
                i2++;
            }
        }
        return result;
    }
};