Create check-if-array-pairs-are-divisible-by-k.cpp

Author: kamyu104

C++/check-if-array-pairs-are-divisible-by-k.cpp

@@ -0,0 +1,22 @@
+// Time:  O(n)
+// Space: O(k)
+
+class Solution {
+public:
+    bool canArrange(vector<int>& arr, int k) {
+        if (arr.size() % 2) {
+            return false;
+        }
+        unordered_map<int, int> count;
+        for (const auto& i : arr) {
+            ++count[(i % k + k) % k];
+        }
+        for (int i = 0; i < k; ++i) {
+            if ((!i && count[i] % 2) ||
+                (i && count[i] != count[k - i])) {
+                    return false;
+            }
+        }
+        return true;
+    }
+};