問題
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].
制約
0 ≤ pushes ≤ 10^7
1 ≤ initial_capacity ≤ 10^6
例
入力：
pushes = 5
initial_capacity = 1
期待される出力：
expected = [3, 7, 8]入力：
long long pushes = 5;
long long initial_capacity = 1;
期待される出力：
std::vector<long long> expected = {3, 7, 8};入力：
long pushes = 5;
long initial_capacity = 1;
期待される出力：
long[] expected = new long[] {3, 7, 8};解説
Capacity grows 1 → 2 → 4 → 8 when pushing the 2nd, 3rd and 5th elements, copying 1 + 2 + 4 = 7 elements: [3, 7, 8].
入力：
pushes = 4
initial_capacity = 4
期待される出力：
expected = [0, 0, 4]入力：
long long pushes = 4;
long long initial_capacity = 4;
期待される出力：
std::vector<long long> expected = {0, 0, 4};入力：
long pushes = 4;
long initial_capacity = 4;
期待される出力：
long[] expected = new long[] {0, 0, 4};解説
All four elements fit in the first block, so nothing is reallocated: [0, 0, 4].
解き方のヒント
まずは自分で考えてから、ヒントを 1 つずつ開いてみましょう。
ヒント 1
A reallocation happens only when the array is full.
ヒント 2
Each time, all current elements are copied and the capacity doubles.
ヒント 3
You can jump from one doubling to the next instead of simulating every push.
目安の計算量
O(log pushes) time, O(1) extra space
参考資料
この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。