g2501_2600.s2502_design_memory_allocator.Allocator

public class Allocator extends Object

2502 - Design Memory Allocator.Medium You are given an integer <code>n</code> representing the size of a 0-indexed memory array. All memory units are initially free. You have a memory allocator with the following functionalities: <ol> <li>Allocate a block of <code>size</code> consecutive free memory units and assign it the id <code>mID</code>.</li> <li>Free all memory units with the given id <code>mID</code>.</li> </ol> Note that: <ul> <li>Multiple blocks can be allocated to the same <code>mID</code>.</li> <li>You should free all the memory units with <code>mID</code>, even if they were allocated in different blocks.</li> </ul> Implement the <code>Allocator</code> class: <ul> <li><code>Allocator(int n)</code> Initializes an <code>Allocator</code> object with a memory array of size <code>n</code>.</li> <li><code>int allocate(int size, int mID)</code> Find the leftmost block of <code>size</code> consecutive free memory units and allocate it with the id <code>mID</code>. Return the block’s first index. If such a block does not exist, return <code>-1</code>.</li> <li><code>int free(int mID)</code> Free all memory units with the id <code>mID</code>. Return the number of memory units you have freed.</li> </ul> Example 1: Input [“Allocator”, “allocate”, “allocate”, “allocate”, “free”, “allocate”, “allocate”, “allocate”, “free”, “allocate”, “free”] [[10], [1, 1], [1, 2], [1, 3], [2], [3, 4], [1, 1], [1, 1], [1], [10, 2], [7]] Output: [null, 0, 1, 2, 1, 3, 1, 6, 3, -1, 0] Explanation: Allocator loc = new Allocator(10); // Initialize a memory array of size 10. All memory units are initially free. loc.allocate(1, 1); // The leftmost block’s first index is 0. The memory array becomes [1 ,_,_,_,_,_,_,_,_,_]. We return 0. loc.allocate(1, 2); // The leftmost block’s first index is 1. The memory array becomes [1, 2 ,_,_,_,_,_,_,_,_]. We return 1. loc.allocate(1, 3); // The leftmost block’s first index is 2. The memory array becomes [1,2, 3 ,_,_,_,_,_,_,_]. We return 2. loc.free(2); // Free all memory units with mID 2. The memory array becomes [1,_, 3,_,_,_,_,_,_,_]. We return 1 since there is only 1 unit with mID 2. loc.allocate(3, 4); // The leftmost block’s first index is 3. The memory array becomes [1,_,3, 4 , 4 , 4 ,_,_,_,_]. We return 3. loc.allocate(1, 1); // The leftmost block’s first index is 1. The memory array becomes [1, 1 ,3,4,4,4,_,_,_,_]. We return 1. loc.allocate(1, 1); // The leftmost block’s first index is 6. The memory array becomes [1,1,3,4,4,4, 1 ,_,_,_]. We return 6. loc.free(1); // Free all memory units with mID 1. The memory array becomes [_,_,3,4,4,4,_,_,_,_]. We return 3 since there are 3 units with mID 1. loc.allocate(10, 2); // We can not find any free block with 10 consecutive free memory units, so we return -1. loc.free(7); // Free all memory units with mID 7. The memory array remains the same since there is no memory unit with mID 7. We return 0. Constraints: <ul> <li><code>1 <= n, size, mID <= 1000</code></li> <li>At most <code>1000</code> calls will be made to <code>allocate</code> and <code>free</code>.</li> </ul>

Constructor Summary

Constructors

Constructor

Description

Allocator(int n)
Method Summary

Modifier and Type

Method

Description

int

allocate(int size, int mID)

int

collapse(g2501_2600.s2502_design_memory_allocator.Allocator.Node cur, int id)

int

free(int mID)

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details
- Allocator
  
  public Allocator(int n)
Method Details
- allocate
  
  public int allocate(int size, int mID)
- free
  
  public int free(int mID)
- collapse
  
  public int collapse(g2501_2600.s2502_design_memory_allocator.Allocator.Node cur, int id)

Class Allocator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Details

Allocator

Method Details

allocate

free

collapse