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This approach involves iterating over each element of the array, applying the provided function to determine the key for each element, and then organizing elements in an object based on these keys.
Time Complexity: O(n * m) where n is the number of elements and m is the average length of strings (due to strcmp operation).
Space Complexity: O(n) for storage of key-value mappings.
1
The Java implementation employs a HashMap to associate keys, derived by applying the function, with lists of elements. computeIfAbsent is used for efficient map population.
This approach recursively divides the array, processes elements with memoization to store previously encountered keys, thus reducing redundant calculations, which optimizes processing of large arrays.
Time Complexity: O(n * m), where m is affected by recursion depth.
Space Complexity: O(n) for memo storage and call stack.
1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4
5typedef struct KeyValue {
6 char *key;
7 void **values;
8 size_t size;
9} KeyValue;
10
11KeyValue * recursiveGroupBy(void **arr, size_t size, char *(*fn)(void*), size_t *resultSize) {
12 // Recursive grouping logic with memoization should be implemented here
13}In this recursive implementation, the function would conceptually keep a cache of already encountered keys, to avoid recalculating them. As memory allocation and proper recursive function configuration is complex in C, it's a theoretical implementation.