New Problem Solution - "1846. Maximum Element After Decreasing and Rearranging"

Author: haoel

README.md

@@ -9,6 +9,7 @@ LeetCode
 
 | # | Title | Solution | Difficulty |
 |---| ----- | -------- | ---------- |
+|1846|[Maximum Element After Decreasing and Rearranging](https://leetcode.com/problems/maximum-element-after-decreasing-and-rearranging/) | [C++](./algorithms/cpp/maximumElementAfterDecreasingAndRearranging/MaximumElementAfterDecreasingAndRearranging.cpp)|Medium|
 |1845|[Seat Reservation Manager](https://leetcode.com/problems/seat-reservation-manager/) | [C++](./algorithms/cpp/seatReservationManager/SeatReservationManager.cpp)|Medium|
 |1844|[Replace All Digits with Characters](https://leetcode.com/problems/replace-all-digits-with-characters/) | [C++](./algorithms/cpp/replaceAllDigitsWithCharacters/ReplaceAllDigitsWithCharacters.cpp)|Easy|
 |1840|[Maximum Building Height](https://leetcode.com/problems/maximum-building-height/) | [C++](./algorithms/cpp/maximumBuildingHeight/MaximumBuildingHeight.cpp)|Hard|

algorithms/cpp/maximumElementAfterDecreasingAndRearranging/MaximumElementAfterDecreasingAndRearranging.cpp

@@ -0,0 +1,70 @@
+// Source : https://leetcode.com/problems/maximum-element-after-decreasing-and-rearranging/
+// Author : Hao Chen
+// Date   : 2021-05-03
+
+/***************************************************************************************************** 
+ *
+ * You are given an array of positive integers arr. Perform some operations (possibly none) on arr so 
+ * that it satisfies these conditions:
+ * 
+ * 	The value of the first element in arr must be 1.
+ * 	The absolute difference between any 2 adjacent elements must be less than or equal to 1. In 
+ * other words, abs(arr[i] - arr[i - 1]) <= 1 for each i where 1 <= i < arr.length (0-indexed). abs(x) 
+ * is the absolute value of x.
+ * 
+ * There are 2 types of operations that you can perform any number of times:
+ * 
+ * 	Decrease the value of any element of arr to a smaller positive integer.
+ * 	Rearrange the elements of arr to be in any order.
+ * 
+ * Return the maximum possible value of an element in arr after performing the operations to satisfy 
+ * the conditions.
+ * 
+ * Example 1:
+ * 
+ * Input: arr = [2,2,1,2,1]
+ * Output: 2
+ * Explanation: 
+ * We can satisfy the conditions by rearranging arr so it becomes [1,2,2,2,1].
+ * The largest element in arr is 2.
+ * 
+ * Example 2:
+ * 
+ * Input: arr = [100,1,1000]
+ * Output: 3
+ * Explanation: 
+ * One possible way to satisfy the conditions is by doing the following:
+ * 1. Rearrange arr so it becomes [1,100,1000].
+ * 2. Decrease the value of the second element to 2.
+ * 3. Decrease the value of the third element to 3.
+ * Now arr = [1,2,3], which satisfies the conditions.
+ * The largest element in arr is 3.
+ * 
+ * Example 3:
+ * 
+ * Input: arr = [1,2,3,4,5]
+ * Output: 5
+ * Explanation: The array already satisfies the conditions, and the largest element is 5.
+ * 
+ * Constraints:
+ * 
+ * 	1 <= arr.length <= 10^5
+ * 	1 <= arr[i] <= 10^9
+ ******************************************************************************************************/
+
+class Solution {
+public:
+    int maximumElementAfterDecrementingAndRearranging(vector<int>& arr) {
+        sort(arr.begin(), arr.end());
+        int m = arr[0] = 1;
+        for(int i=0; i<arr.size()-1; i++) {
+            if (abs(arr[i] - arr[i+1]) <= 1) {
+                m = max(arr[i], arr[i+1]);
+                continue;
+            }
+            arr[i+1] = arr[i] + 1;
+            m = arr[i+1];
+        }
+        return m;
+    }
+};