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Program to Find Out a Sequence with Equivalent Frequencies in Python
Suppose we have a list of numbers. We have to find the length of the longest sequence of numbers such that when we delete a number from the sequence, each number occurs the same number of times.
So, if the input is like numbers = [2, 4, 4, 7, 7, 6, 6], then the output will be 7.
To solve this, we will follow these steps −
num_freq := a new map
freq_freq := a new map
diff_freq := a new set
result := 1
for each index I and value num in nums, do
cur_freq := num_freq[num]
num_freq[num] := num_freq[num] + 1
freq_freq[cur_freq] := freq_freq[cur_freq] − 1
freq_freq[cur_freq + 1] := freq_freq[cur_freq + 1] + 1
add cur_freq + 1 into diff_freq
if cur_freq is in diff_freq, and freq_freq[cur_freq] is same as 0, then
delete cur_freq from diff_freq
df_list := a new list by taking elements of diff_freqs
if size of df_list is same as 1, then
result := i + 1
otherwise when size of df_list is same as 2, and (when any of [|freq_freq[df_list[0]] - freq_freq[df_list[1]]| ,freq_freq[df_list[0]], freq_freq[df_list[1]] ) is 1 ), and (when any of [|df_list[0] - df_list[1]|, df_list[0], df_list[1]]) is 1), then
result := i + 1
return result
Let us see the following implementation to get better understanding −
Example
from collections import defaultdict class Solution: def solve(self, nums): num_freq = defaultdict(int) freq_freq = defaultdict(int) diff_freq = set() result = 1 for i, num in enumerate(nums): cur_freq = num_freq[num] num_freq[num] += 1 freq_freq[cur_freq] −= 1 freq_freq[cur_freq + 1] += 1 diff_freq.add(cur_freq + 1) if cur_freq in diff_freq and freq_freq[cur_freq] == 0: diff_freq.remove(cur_freq) df_list = list(diff_freq) if len(df_list) == 1: result = i + 1 elif ( len(df_list) == 2 and any( x == 1 for x in [ abs(freq_freq[df_list[0]] − freq_freq[df_list[1]]), freq_freq[df_list[0]], freq_freq[df_list[1]], ] ) and any(x == 1 for x in [abs(df_list[0] − df_list[1]), df_list[0], df_list[1]]) ): result = i + 1 return result ob = Solution() print(ob.solve([2, 4, 4, 7, 7, 6, 6]))
Input
numbers = [2, 4, 4, 7, 7, 6, 6]
Output
7
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