day 11

Author: sachuverma

Leetcode Daily Challenge/August-2021/11. Array of Doubled Pairs.cpp

@@ -0,0 +1,79 @@
+/*
+Array of Doubled Pairs
+======================
+
+Given an integer array of even length arr, return true if it is possible to reorder arr such that arr[2 * i + 1] = 2 * arr[2 * i] for every 0 <= i < len(arr) / 2, or false otherwise.
+
+Example 1:
+Input: arr = [3,1,3,6]
+Output: false
+
+Example 2:
+Input: arr = [2,1,2,6]
+Output: false
+
+Example 3:
+Input: arr = [4,-2,2,-4]
+Output: true
+Explanation: We can take two groups, [-2,-4] and [2,4] to form [-2,-4,2,4] or [2,4,-2,-4].
+
+Example 4:
+Input: arr = [1,2,4,16,8,4]
+Output: false
+ 
+Constraints:
+2 <= arr.length <= 3 * 104
+arr.length is even.
+-105 <= arr[i] <= 105
+*/
+
+class Solution
+{
+public:
+    bool canReorderDoubled(vector<int> &arr)
+    {
+
+        map<int, int> nums;
+        for (auto &i : arr)
+            nums[i]++;
+
+        while (nums.size() > 0)
+        {
+            int least = (*nums.begin()).first;
+            int target;
+
+            if (least == 0)
+            {
+                if (nums[least] % 2 != 0)
+                    return false;
+                nums.erase(least);
+            }
+
+            else
+            {
+
+                if (least < 0)
+                {
+                    if (least % 2 != 0)
+                        return false;
+                    target = least / 2;
+                }
+                else
+                    target = 2 * least;
+
+                int mi = min(nums[target], nums[least]);
+                if (mi == 0)
+                    return false;
+
+                nums[target] -= mi;
+                nums[least] -= mi;
+
+                if (!nums[target])
+                    nums.erase(target);
+                if (!nums[least])
+                    nums.erase(least);
+            }
+        }
+        return true;
+    }
+};

Leetcode Daily Challenge/August-2021/README.md

@@ -12,4 +12,5 @@
 | 7.  | [Palindrome Partitioning II](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/613/week-1-august-1st-august-7th/3872/)               |        [cpp](./07.%20Palindrome%20Partitioning%20II.cpp)        |
 | 9.  | [Add Strings](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/614/week-2-august-8th-august-14th/3875/)                             |                [cpp](./09.%20Add%20Strings.cpp)                 |
 | 10. | [Flip String to Monotone Increasing](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/614/week-2-august-8th-august-14th/3876/)      |  [cpp](./10.%20Flip%20String%20to%20Monotone%20Increasing.cpp)  |
+| 11. | [Array of Doubled Pairs](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/614/week-2-august-8th-august-14th/3877/)                  |         [cpp](./11.%20Array%20of%20Doubled%20Pairs.cpp)         |
 | 12. | [Group Anagrams](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge-2021/614/week-2-august-8th-august-14th/3887/)                          |               [cpp](./12.%20Group%20Anagrams.cpp)               |