Create array-of-doubled-pairs.cpp

Author: kamyu104

C++/array-of-doubled-pairs.cpp

@@ -0,0 +1,27 @@
+// Time:  O(n + klogk)
+// Space: O(k)
+
+class Solution {
+public:
+    bool canReorderDoubled(vector<int>& A) {
+        unordered_map<int, int> count;
+        for (const auto& x : A) {
+            ++count[x];
+        }
+        vector<int> keys;
+        for (const auto& kvp : count) {
+            keys.emplace_back(kvp.first);
+        }
+        sort(keys.begin(), keys.end(),
+             [](int i, int j) {
+                 return abs(i) < abs(j);
+             });
+        for (const auto& x : keys) {
+            if (count[x] > count[2 * x]) {
+                return false;
+            }
+            count[2 * x] -= count[x];
+        }
+        return true;
+    }
+};