Snapshot Array

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Problem Statement

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

Examples

Example 1

Input: ["SnapshotArray","set","snap","set","get"]
[[3],[0,5],[],[0,6],[0,0]]
Output: [null,null,0,null,5]
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 <= 5 * 10 ^4

0 <= index < length

0 <= val <= 10 ^9

0 <= snap_id < (the total number of times we call snap() )

At most 5 * 10 ^4 calls will be made to set , snap , and get .

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicHash Table