Circular buffers are simple data structures that provide O(1) get
, set
, append
, prepend
, clear
, dropFirst
and dropLast
operations. It can be implemented using 2 pointers (start
and end
) and an array and using modular arithmetics for indexing.
Here is a simple implementation in Java:
class CircularBuffer<T> {
private T[] array = (T[]) new Object[1<<4];
private int start = 0, end = 0;
public T get(int i) {
assert(0 <= i && i < size());
return array[mod(start + i)];
}
public void set(int i, T elem) {
assert(0 <= i && i < size());
array[mod(start + i)] = elem;
}
public void append(T elem) {
if (size() == array.length - 1) resize();
array[mod(end++)] = elem;
}
public void prepend(T elem) {
if (size() == array.length - 1) resize();
array[mod(--start)] = elem;
}
public void dropFirst(int count) {
assert(0 <= count && count <= size());
start += count;
}
public void dropLast(int count) {
assert(0 <= count && count <= size());
end -= count;
}
public int size() {
return mod(mod(end) - mod(start));
}
public void clear() {
start = end;
}
private int mod(int x) {
return Math.floorMod(x, array.length);
}
private void resize() {
T[] array2 = (T[]) new Object[2*array.length];
for(int i = 0; i < size(); i++) {
array2[i] = get(i);
}
end = size();
start = 0;
array = array2;
}
}
Source: https://gist.github.com/pathikrit/eac29538af53abf7e827a74e110fb0ac