LeetCode [1146] Snapshot Array

 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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

class SnapshotArray { TreeMap<Integer, Integer>[] ss; int snap_id = 0; public SnapshotArray(int length) { ss = new TreeMap[length]; for(int i=0; i<length; ++i) { ss[i] = new TreeMap<Integer, Integer>(); ss[i].put(0, 0); } } public void set(int index, int val) { ss[index].put(snap_id, val); } public int snap() { return snap_id++; } public int get(int index, int snap_id) { return ss[index].floorEntry(snap_id).getValue(); } public static void main(String[] args) { System.out.println("Hi"); } } /** * Your SnapshotArray object will be instantiated and called as such: * SnapshotArray obj = new SnapshotArray(length); * obj.set(index,val); * int param_2 = obj.snap(); * int param_3 = obj.get(index,snap_id); */