Problema
A dynamic array such as C++ std::vector stores its elements in one block of memory. When the block is full and a new element arrives, it allocates a block twice as large, copies the existing elements over, and frees the old one.
Start with an empty array of capacity initial_capacity and push pushes elements one by one. Before each push, if size == capacity, reallocate: count one reallocation, add the current size to the copied elements, and double the capacity.
Implement dynamic_array_growth(pushes, initial_capacity).
Input
pushes: How many elements are pushed.
initial_capacity: The capacity of the empty array.
Output
Return [reallocations, copied_elements, final_capacity].
Vincoli
0 ≤ pushes ≤ 10^7
1 ≤ initial_capacity ≤ 10^6
Esempi
Input:
pushes = 5
initial_capacity = 1
Output atteso:
expected = [3, 7, 8]Input:
long long pushes = 5;
long long initial_capacity = 1;
Output atteso:
std::vector<long long> expected = {3, 7, 8};Input:
long pushes = 5;
long initial_capacity = 1;
Output atteso:
long[] expected = new long[] {3, 7, 8};Spiegazione
Capacity grows 1 → 2 → 4 → 8 when pushing the 2nd, 3rd and 5th elements, copying 1 + 2 + 4 = 7 elements: [3, 7, 8].
Input:
pushes = 4
initial_capacity = 4
Output atteso:
expected = [0, 0, 4]Input:
long long pushes = 4;
long long initial_capacity = 4;
Output atteso:
std::vector<long long> expected = {0, 0, 4};Input:
long pushes = 4;
long initial_capacity = 4;
Output atteso:
long[] expected = new long[] {0, 0, 4};Spiegazione
All four elements fit in the first block, so nothing is reallocated: [0, 0, 4].
Come affrontarlo
Prova prima da solo, poi apri un suggerimento alla volta.
Suggerimento 1
A reallocation happens only when the array is full.
Suggerimento 2
Each time, all current elements are copied and the capacity doubles.
Suggerimento 3
You can jump from one doubling to the next instead of simulating every push.
Complessità attesa
O(log pushes) time, O(1) extra space
Riferimenti
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