Design a data structure that supports the following operations in O(1) time:
get(index: int) -> int: Retrieve the value at the specified index.
set(index: int, value: int): Update the value at the specified index.
set_all(value: int): Set all elements in the data structure to the specified value.
Requirements:
The data structure should be initialized with a fixed size, and all elements should initially be set to 0.
If set_all is called, subsequent get operations should return the globally set value unless the specific index has been updated after the set_all operation.
d = DataStructure(1000)
print(d.get(950)) # Output: 0
d.set(930, 5)
print(d.get(930)) # Output: 5
d.set_all(8)
print(d.get(950)) # Output: 8
print(d.get(930)) # Output: 8
d.set(910, 7)
print(d.get(910)) # Output: 7
print(d.get(10)) # Output: 8