change file name

leetcode/p1929_concatenationofarray.cpp

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+// basic approach: use two loops to generate the first half and the second half
+/*
+class Solution {
+public:
+    vector<int> getConcatenation(vector<int>& nums) {
+        // use the default constructor
+        vector<int> ans;
+        int size = nums.size();
+        for(int i=0;i<size;i++){
+            ans.push_back(nums[i]);
+        }
+        // do it one more time
+        for(int i=0;i<size;i++){
+            ans.push_back(nums[i]);
+        }
+
+        return ans;
+    }
+};
+*/
+
+// approach 2: use the copy constructor
+
+class Solution {
+public:
+    vector<int> getConcatenation(vector<int>& nums) {
+        // use the copy constructor
+        vector<int> ans(nums);
+        int size = nums.size();
+        // copy the second half
+        for(int i=0;i<size;i++){
+            ans.push_back(nums[i]);
+        }
+
+        return ans;
+    }
+};