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
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
type Pair = (usize, i32);
struct SnapshotArray {
size: usize,
data: Vec<Vec<Pair>>,
snap_id: usize,
}
impl SnapshotArray {
fn new(length: i32) -> Self {
let size = length as usize;
let data = vec![vec![(0, 0)]; size];
let snap_id = 0;
SnapshotArray {
size,
data,
snap_id,
}
}
fn set(&mut self, index: i32, val: i32) {
let i = index as usize;
if let Some(last) = self.data[i].pop() {
if last.0 != self.snap_id {
self.data[i].push(last);
}
}
self.data[i].push((self.snap_id, val));
}
fn snap(&mut self) -> i32 {
self.snap_id += 1;
(self.snap_id - 1) as i32
}
fn get(&self, index: i32, snap_id: i32) -> i32 {
let i = index as usize;
let snap_id = snap_id as usize;
match self.data[i].binary_search_by_key(&snap_id, |p| p.0) {
Ok(j) => self.data[i][j].1,
Err(j) => self.data[i][j - 1].1,
}
}
}
#[test]
fn test() {
let mut obj = SnapshotArray::new(3);
obj.set(0, 5);
assert_eq!(obj.snap(), 0);
obj.set(0, 6);
assert_eq!(obj.get(0, 0), 5);
}