Create find-the-difference-of-two-arrays.cpp

Author: kamyu104

C++/find-the-difference-of-two-arrays.cpp

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+// Time:  O(n)
+// Space: O(n)
+
+// hash table
+class Solution {
+public:
+    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {
+        vector<vector<int>> result(2);
+        vector<unordered_set<int>> lookup = {{cbegin(nums1), cend(nums1)}, {cbegin(nums2), cend(nums2)}};
+        for (int i = 0; i < 2; ++i) {
+            for (const auto& x : lookup[i]) {
+                if (!lookup[1 - i].count(x)) {
+                    result[i].emplace_back(x);
+                }
+            }
+        }
+        return result;
+    }
+};