Python C++採陣列排序速解字串問題Leetcode 451 Sort Characters By Frequency

解Leetcode 451. Sort Characters By Frequency.兩個重點，一是可用陣列就不用hash table(C++ unordered_map)來計數，二是排序的元素很少，可以練習各種排序法，用sort，自製radix sort，用max heap(C++ priority_queue)

Python C++採陣列排序速解字串問題Leetcode 451  Sort Characters By Frequency

1. 頻率計數儲存在freq中

2. 使用陣列 freq_c`迭代來收集 ['0', 'z'] 的資訊 (freq[c-'0'], c)

3. 使用 sort 依照 greater 順序對 freq_c 進行排序

4. 使用字串函數來完成工作並傳回 ans

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1. The frequency count is stored in freq

2. Use array freq_c` iteration to collect information of ['0', 'z'] (freq[c-'0'], c)

3. Use sort to sort freq_c in greater order

4. Use string functions to do the work and return ans

[codes on Leetcode]https://leetcode.com/problems/sort-characters-by-frequency/solutions/4689181/just-arrays-3-kinds-of-sortings-no-hash-table-0ms-beats-100/

[Leetcode playList]https://www.youtube.com/watch?v=FrnktWsWFeQ&list=PLYRlUBnWnd5IdDHk2BjqXwesydU17z_xk

[Dynamic Programming Playlist]https://www.youtube.com/watch?v=30yq3fmE6E8&list=PLYRlUBnWnd5K_XYUesV9oc6M9ONXII61T