C# Solution for Sort Array In Increasing Frequency Problem
Intuition\n Describe your first thoughts on how to solve this problem. \nIn C#, we can use a Dictionary for counting frequencies, followed by a sorted list to m
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\nIn C#, we can use a Dictionary for counting frequencies, followed by a sorted list to maintain the elements by their frequency. Here\u2019s\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n1.\tCount Frequencies: Use a Dictionary<int, int> to store the frequency of each element.\n2.\tGroup by Frequency: Use another Dictionary<int, List<int>> to group elements by their frequency.\n3.\tSort Groups: Sort the keys of the frequency groups in ascending order and within each frequency group, sort the elements in descending order.\n4.\tConstruct Result: Iterate over the sorted frequency groups to construct the result array.\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n1.\tCounting Frequencies: This takes  O(n)  time.\n2.\tGrouping by Frequency: This takes  O(n)  time.\n3.\tSorting Groups: Sorting the frequency keys takes  O(k log k) , where  k  is the number of unique frequencies. Sorting the elements within each frequency group takes  O(u log u)  for each group, where  u  is the number of unique elements with that frequency. In the worst case, this can be  O(n log n) .\n4.\tConstructing Result: This takes  O(n)  time.\n\nThus, the overall time complexity is  O(n log n) .\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n1.\tDictionary for Frequency Count: This requires  O(n)  space in the worst case.\n2.\tDictionary for Grouping by Frequency: This also requires  O(n)  space.\n3.\tList for Sorted Numbers: This requires  O(n)  space.\n\nThus, the overall space complexity is  O(n) .\n\n# Code\n```\npublic class Solution {\n    public int[] FrequencySort(int[] nums) {\n        // Step 1: Count the frequency of each element\n        var freqMap = new Dictionary<int, int>();\n        foreach (var num in nums) {\n            if (freqMap.ContainsKey(num)) {\n                freqMap[num]++;\n            } else {\n                freqMap[num] = 1;\n            }\n        }\n\n        // Step 2: Group elements by their frequency\n        var groupedByFreq = new Dictionary<int, List<int>>();\n        foreach (var kvp in freqMap) {\n            var num = kvp.Key;\n            var freq = kvp.Value;\n            if (!groupedByFreq.ContainsKey(freq)) {\n                groupedByFreq[freq] = new List<int>();\n            }\n            groupedByFreq[freq].Add(num);\n        }\n\n        // Step 3: Sort the groups by frequency and sort the elements in each group in descending order\n        var sortedNums = new List<int>();\n        foreach (var freq in groupedByFreq.Keys.OrderBy(f => f)) {\n            var numsWithSameFreq = groupedByFreq[freq];\n            numsWithSameFreq.Sort((a, b) => b.CompareTo(a)); // Descending order\n            foreach (var num in numsWithSameFreq) {\n                for (int i = 0; i < freq; i++) {\n                    sortedNums.Add(num);\n                }\n            }\n        }\n\n        return sortedNums.ToArray();\n    }\n}\n```
['C#']