Create array_of_doubled_pairs.cpp

Author: avidLearnerInProgress

array_of_doubled_pairs.cpp

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+class Solution {
+public:
+    bool canReorderDoubled(vector<int>& arr) {
+        if(arr.size() == 0) return true;
+        
+        unordered_map<int, int> ump; //element to count
+        sort(arr.begin(), arr.end());
+        
+        for(auto element : arr) {
+            ump[element]++;
+        }
+        
+        for(auto element: arr) {
+            if (ump[element] == 0) {
+                continue;
+            }
+            if (element < 0 && element % 2 != 0) { //for -ve values, there is no element/2 pair to match
+                return false;
+            }
+            int pair = element > 0 ? element*2 : element/2; //positive or negative
+            if (ump[pair] == 0) { //no match with element
+                return false;
+            }
+            ump[element]--;
+            ump[pair]--;
+        }
+        return true;
+    }
+};