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Rollup merge of #58421 - nox:relax-bounds-binary-heap, r=dtolnay

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Relax some Ord bounds on BinaryHeap<T>

Notably, iterators don't require any trait bounds to be iterated.
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Mazdak Farrokhzad 2019-02-25 03:18:01 +01:00 committed by GitHub
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src/liballoc/collections/binary_heap.rs
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@ -294,7 +294,7 @@ impl<T: Ord> Default for BinaryHeap<T> {
} }
#[stable(feature = "binaryheap_debug", since = "1.4.0")] #[stable(feature = "binaryheap_debug", since = "1.4.0")]
impl<T: fmt::Debug + Ord> fmt::Debug for BinaryHeap<T> { impl<T: fmt::Debug> fmt::Debug for BinaryHeap<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self.iter()).finish() f.debug_list().entries(self.iter()).finish()
} }
@ -336,6 +336,258 @@ impl<T: Ord> BinaryHeap<T> {
BinaryHeap { data: Vec::with_capacity(capacity) } BinaryHeap { data: Vec::with_capacity(capacity) }
} }
/// Returns a mutable reference to the greatest item in the binary heap, or
/// `None` if it is empty.
///
/// Note: If the `PeekMut` value is leaked, the heap may be in an
/// inconsistent state.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::new();
/// assert!(heap.peek_mut().is_none());
///
/// heap.push(1);
/// heap.push(5);
/// heap.push(2);
/// {
/// let mut val = heap.peek_mut().unwrap();
/// *val = 0;
/// }
/// assert_eq!(heap.peek(), Some(&2));
/// ```
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> {
if self.is_empty() {
None
} else {
Some(PeekMut {
heap: self,
sift: true,
})
}
}
/// Removes the greatest item from the binary heap and returns it, or `None` if it
/// is empty.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::from(vec![1, 3]);
///
/// assert_eq!(heap.pop(), Some(3));
/// assert_eq!(heap.pop(), Some(1));
/// assert_eq!(heap.pop(), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop(&mut self) -> Option<T> {
self.data.pop().map(|mut item| {
if !self.is_empty() {
swap(&mut item, &mut self.data[0]);
self.sift_down_to_bottom(0);
}
item
})
}
/// Pushes an item onto the binary heap.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::new();
/// heap.push(3);
/// heap.push(5);
/// heap.push(1);
///
/// assert_eq!(heap.len(), 3);
/// assert_eq!(heap.peek(), Some(&5));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push(&mut self, item: T) {
let old_len = self.len();
self.data.push(item);
self.sift_up(0, old_len);
}
/// Consumes the `BinaryHeap` and returns a vector in sorted
/// (ascending) order.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
///
/// let mut heap = BinaryHeap::from(vec![1, 2, 4, 5, 7]);
/// heap.push(6);
/// heap.push(3);
///
/// let vec = heap.into_sorted_vec();
/// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);
/// ```
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
pub fn into_sorted_vec(mut self) -> Vec<T> {
let mut end = self.len();
while end > 1 {
end -= 1;
self.data.swap(0, end);
self.sift_down_range(0, end);
}
self.into_vec()
}
// The implementations of sift_up and sift_down use unsafe blocks in
// order to move an element out of the vector (leaving behind a
// hole), shift along the others and move the removed element back into the
// vector at the final location of the hole.
// The `Hole` type is used to represent this, and make sure
// the hole is filled back at the end of its scope, even on panic.
// Using a hole reduces the constant factor compared to using swaps,
// which involves twice as many moves.
fn sift_up(&mut self, start: usize, pos: usize) -> usize {
unsafe {
// Take out the value at `pos` and create a hole.
let mut hole = Hole::new(&mut self.data, pos);
while hole.pos() > start {
let parent = (hole.pos() - 1) / 2;
if hole.element() <= hole.get(parent) {
break;
}
hole.move_to(parent);
}
hole.pos()
}
}
/// Take an element at `pos` and move it down the heap,
/// while its children are larger.
fn sift_down_range(&mut self, pos: usize, end: usize) {
unsafe {
let mut hole = Hole::new(&mut self.data, pos);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
// compare with the greater of the two children
if right < end && !(hole.get(child) > hole.get(right)) {
child = right;
}
// if we are already in order, stop.
if hole.element() >= hole.get(child) {
break;
}
hole.move_to(child);
child = 2 * hole.pos() + 1;
}
}
}
fn sift_down(&mut self, pos: usize) {
let len = self.len();
self.sift_down_range(pos, len);
}
/// Take an element at `pos` and move it all the way down the heap,
/// then sift it up to its position.
///
/// Note: This is faster when the element is known to be large / should
/// be closer to the bottom.
fn sift_down_to_bottom(&mut self, mut pos: usize) {
let end = self.len();
let start = pos;
unsafe {
let mut hole = Hole::new(&mut self.data, pos);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
// compare with the greater of the two children
if right < end && !(hole.get(child) > hole.get(right)) {
child = right;
}
hole.move_to(child);
child = 2 * hole.pos() + 1;
}
pos = hole.pos;
}
self.sift_up(start, pos);
}
fn rebuild(&mut self) {
let mut n = self.len() / 2;
while n > 0 {
n -= 1;
self.sift_down(n);
}
}
/// Moves all the elements of `other` into `self`, leaving `other` empty.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
///
/// let v = vec![-10, 1, 2, 3, 3];
/// let mut a = BinaryHeap::from(v);
///
/// let v = vec![-20, 5, 43];
/// let mut b = BinaryHeap::from(v);
///
/// a.append(&mut b);
///
/// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
/// assert!(b.is_empty());
/// ```
#[stable(feature = "binary_heap_append", since = "1.11.0")]
pub fn append(&mut self, other: &mut Self) {
if self.len() < other.len() {
swap(self, other);
}
if other.is_empty() {
return;
}
#[inline(always)]
fn log2_fast(x: usize) -> usize {
8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1
}
// `rebuild` takes O(len1 + len2) operations
// and about 2 * (len1 + len2) comparisons in the worst case
// while `extend` takes O(len2 * log_2(len1)) operations
// and about 1 * len2 * log_2(len1) comparisons in the worst case,
// assuming len1 >= len2.
#[inline]
fn better_to_rebuild(len1: usize, len2: usize) -> bool {
2 * (len1 + len2) < len2 * log2_fast(len1)
}
if better_to_rebuild(self.len(), other.len()) {
self.data.append(&mut other.data);
self.rebuild();
} else {
self.extend(other.drain());
}
}
}
impl<T> BinaryHeap<T> {
/// Returns an iterator visiting all values in the underlying vector, in /// Returns an iterator visiting all values in the underlying vector, in
/// arbitrary order. /// arbitrary order.
/// ///
@ -379,42 +631,6 @@ impl<T: Ord> BinaryHeap<T> {
self.data.get(0) self.data.get(0)
} }
/// Returns a mutable reference to the greatest item in the binary heap, or
/// `None` if it is empty.
///
/// Note: If the `PeekMut` value is leaked, the heap may be in an
/// inconsistent state.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::new();
/// assert!(heap.peek_mut().is_none());
///
/// heap.push(1);
/// heap.push(5);
/// heap.push(2);
/// {
/// let mut val = heap.peek_mut().unwrap();
/// *val = 0;
/// }
/// assert_eq!(heap.peek(), Some(&2));
/// ```
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> {
if self.is_empty() {
None
} else {
Some(PeekMut {
heap: self,
sift: true,
})
}
}
/// Returns the number of elements the binary heap can hold without reallocating. /// Returns the number of elements the binary heap can hold without reallocating.
/// ///
/// # Examples /// # Examples
@ -528,55 +744,6 @@ impl<T: Ord> BinaryHeap<T> {
self.data.shrink_to(min_capacity) self.data.shrink_to(min_capacity)
} }
/// Removes the greatest item from the binary heap and returns it, or `None` if it
/// is empty.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::from(vec![1, 3]);
///
/// assert_eq!(heap.pop(), Some(3));
/// assert_eq!(heap.pop(), Some(1));
/// assert_eq!(heap.pop(), None);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn pop(&mut self) -> Option<T> {
self.data.pop().map(|mut item| {
if !self.is_empty() {
swap(&mut item, &mut self.data[0]);
self.sift_down_to_bottom(0);
}
item
})
}
/// Pushes an item onto the binary heap.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
/// let mut heap = BinaryHeap::new();
/// heap.push(3);
/// heap.push(5);
/// heap.push(1);
///
/// assert_eq!(heap.len(), 3);
/// assert_eq!(heap.peek(), Some(&5));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push(&mut self, item: T) {
let old_len = self.len();
self.data.push(item);
self.sift_up(0, old_len);
}
/// Consumes the `BinaryHeap` and returns the underlying vector /// Consumes the `BinaryHeap` and returns the underlying vector
/// in arbitrary order. /// in arbitrary order.
/// ///
@ -599,110 +766,6 @@ impl<T: Ord> BinaryHeap<T> {
self.into() self.into()
} }
/// Consumes the `BinaryHeap` and returns a vector in sorted
/// (ascending) order.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
///
/// let mut heap = BinaryHeap::from(vec![1, 2, 4, 5, 7]);
/// heap.push(6);
/// heap.push(3);
///
/// let vec = heap.into_sorted_vec();
/// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);
/// ```
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
pub fn into_sorted_vec(mut self) -> Vec<T> {
let mut end = self.len();
while end > 1 {
end -= 1;
self.data.swap(0, end);
self.sift_down_range(0, end);
}
self.into_vec()
}
// The implementations of sift_up and sift_down use unsafe blocks in
// order to move an element out of the vector (leaving behind a
// hole), shift along the others and move the removed element back into the
// vector at the final location of the hole.
// The `Hole` type is used to represent this, and make sure
// the hole is filled back at the end of its scope, even on panic.
// Using a hole reduces the constant factor compared to using swaps,
// which involves twice as many moves.
fn sift_up(&mut self, start: usize, pos: usize) -> usize {
unsafe {
// Take out the value at `pos` and create a hole.
let mut hole = Hole::new(&mut self.data, pos);
while hole.pos() > start {
let parent = (hole.pos() - 1) / 2;
if hole.element() <= hole.get(parent) {
break;
}
hole.move_to(parent);
}
hole.pos()
}
}
/// Take an element at `pos` and move it down the heap,
/// while its children are larger.
fn sift_down_range(&mut self, pos: usize, end: usize) {
unsafe {
let mut hole = Hole::new(&mut self.data, pos);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
// compare with the greater of the two children
if right < end && !(hole.get(child) > hole.get(right)) {
child = right;
}
// if we are already in order, stop.
if hole.element() >= hole.get(child) {
break;
}
hole.move_to(child);
child = 2 * hole.pos() + 1;
}
}
}
fn sift_down(&mut self, pos: usize) {
let len = self.len();
self.sift_down_range(pos, len);
}
/// Take an element at `pos` and move it all the way down the heap,
/// then sift it up to its position.
///
/// Note: This is faster when the element is known to be large / should
/// be closer to the bottom.
fn sift_down_to_bottom(&mut self, mut pos: usize) {
let end = self.len();
let start = pos;
unsafe {
let mut hole = Hole::new(&mut self.data, pos);
let mut child = 2 * pos + 1;
while child < end {
let right = child + 1;
// compare with the greater of the two children
if right < end && !(hole.get(child) > hole.get(right)) {
child = right;
}
hole.move_to(child);
child = 2 * hole.pos() + 1;
}
pos = hole.pos;
}
self.sift_up(start, pos);
}
/// Returns the length of the binary heap. /// Returns the length of the binary heap.
/// ///
/// # Examples /// # Examples
@ -789,67 +852,6 @@ impl<T: Ord> BinaryHeap<T> {
pub fn clear(&mut self) { pub fn clear(&mut self) {
self.drain(); self.drain();
} }
fn rebuild(&mut self) {
let mut n = self.len() / 2;
while n > 0 {
n -= 1;
self.sift_down(n);
}
}
/// Moves all the elements of `other` into `self`, leaving `other` empty.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// use std::collections::BinaryHeap;
///
/// let v = vec![-10, 1, 2, 3, 3];
/// let mut a = BinaryHeap::from(v);
///
/// let v = vec![-20, 5, 43];
/// let mut b = BinaryHeap::from(v);
///
/// a.append(&mut b);
///
/// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
/// assert!(b.is_empty());
/// ```
#[stable(feature = "binary_heap_append", since = "1.11.0")]
pub fn append(&mut self, other: &mut Self) {
if self.len() < other.len() {
swap(self, other);
}
if other.is_empty() {
return;
}
#[inline(always)]
fn log2_fast(x: usize) -> usize {
8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1
}
// `rebuild` takes O(len1 + len2) operations
// and about 2 * (len1 + len2) comparisons in the worst case
// while `extend` takes O(len2 * log_2(len1)) operations
// and about 1 * len2 * log_2(len1) comparisons in the worst case,
// assuming len1 >= len2.
#[inline]
fn better_to_rebuild(len1: usize, len2: usize) -> bool {
2 * (len1 + len2) < len2 * log2_fast(len1)
}
if better_to_rebuild(self.len(), other.len()) {
self.data.append(&mut other.data);
self.rebuild();
} else {
self.extend(other.drain());
}
}
} }
/// Hole represents a hole in a slice i.e., an index without valid value /// Hole represents a hole in a slice i.e., an index without valid value
@ -1111,7 +1113,7 @@ impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
} }
#[stable(feature = "rust1", since = "1.0.0")] #[stable(feature = "rust1", since = "1.0.0")]
impl<T: Ord> IntoIterator for BinaryHeap<T> { impl<T> IntoIterator for BinaryHeap<T> {
type Item = T; type Item = T;
type IntoIter = IntoIter<T>; type IntoIter = IntoIter<T>;
@ -1139,9 +1141,7 @@ impl<T: Ord> IntoIterator for BinaryHeap<T> {
} }
#[stable(feature = "rust1", since = "1.0.0")] #[stable(feature = "rust1", since = "1.0.0")]
impl<'a, T> IntoIterator for &'a BinaryHeap<T> impl<'a, T> IntoIterator for &'a BinaryHeap<T> {
where T: Ord
{
type Item = &'a T; type Item = &'a T;
type IntoIter = Iter<'a, T>; type IntoIter = Iter<'a, T>;