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 givenindex
to be equal toval
. -
int snap()
takes a snapshot of the array and returns thesnap_id
: the total number of times we calledsnap()
minus1
. -
int get(index, snap_id)
returns the value at the givenindex
, at the time we took the snapshot with the givensnap_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 toset
,snap
, andget
. -
0 <= index < length
-
0 <= snap_id <
(the total number of times we callsnap()
) -
0 <= val <= 10^9
SOLUTION:
class SnapshotArray:
def __init__(self, length: int):
self.snaps = {}
self.sid = 0
self.n = length
def set(self, index: int, val: int) -> None:
self.snaps[(self.sid, index)] = val
def snap(self) -> int:
res = self.sid
self.sid += 1
return res
def getSnap(self, snap_id, index):
for i in range(snap_id, -1, -1):
if (i, index) in self.snaps:
return self.snaps[(i, index)]
return 0
def get(self, index: int, snap_id: int) -> int:
return self.getSnap(snap_id, index)
# Your SnapshotArray object will be instantiated and called as such:
# obj = SnapshotArray(length)
# obj.set(index,val)
# param_2 = obj.snap()
# param_3 = obj.get(index,snap_id)
Top comments (0)