g1101_1200.s1146_snapshot_array

Class SnapshotArray

java.lang.Object

g1101_1200.s1146_snapshot_array.SnapshotArray

public class SnapshotArray
extends Object

1146 - Snapshot Array.

Medium

Implement a SnapshotArray that supports the following interface:

• SnapshotArray(int length) initializes an array-like data structure with the given length. Initially, each element equals 0.
• void set(index, val) sets the element at the given index to be equal to val.
• int snap() takes a snapshot of the array and returns the snap_id: the total number of times we called snap() minus 1.
• int get(index, snap_id) returns the value at the given index, at the time we took the snapshot with the given snap_id

Example 1:

Input: [“SnapshotArray”,“set”,“snap”,“set”,“get”] [[3],[0,5],[],[0,6],[0,0]]

Output: [null,null,0,null,5]

Explanation:

SnapshotArray snapshotArr = new SnapshotArray(3); // set the length to be 3 snapshotArr.set(0,5); // Set array[0] = 5 snapshotArr.snap(); // Take a snapshot, return snap_id = 0 snapshotArr.set(0,6); snapshotArr.get(0,0); // Get the value of array[0] with snap_id = 0, return 5

Constraints:

• 1 <= length <= 50000
• At most 50000 calls will be made to set, snap, and get.
• 0 <= index < length
• 0 <= snap_id <(the total number of times we call snap())
• 0 <= val <= 10^9

Constructor Summary

Constructors

Constructor and Description
SnapshotArray(int length)

Method Summary

Modifier and Type	Method and Description
int	get(int index, int snapId)
void	set(int index, int val)
int	snap()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SnapshotArray

public SnapshotArray(int length)

Method Detail

set

public void set(int index,
                int val)

snap

public int snap()

get

public int get(int index,
               int snapId)