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replace linearSearch with mem.indexOfScalar, return not found error, factor out siftUp from addUnchecked, use compareFn to decide siftUp/siftDown

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This commit is contained in:
Bhargav Srinivasan 2020-09-22 03:46:13 -07:00
parent a5140cc902
commit 983830a4ae
1 changed files with 13 additions and 20 deletions
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33
lib/std/priority_queue.zig
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@ -49,7 +49,12 @@ pub fn PriorityQueue(comptime T: type) type {
fn addUnchecked(self: *Self, elem: T) void {
self.items[self.len] = elem;
var child_index = self.len;
siftUp(self, self.len);
self.len += 1;
}
fn siftUp(self: *Self, start_index: usize) void {
var child_index = start_index;
while (child_index > 0) {
var parent_index = ((child_index - 1) >> 1);
const child = self.items[child_index];
@ -61,7 +66,6 @@ pub fn PriorityQueue(comptime T: type) type {
self.items[child_index] = parent;
child_index = parent_index;
}
self.len += 1;
}
/// Add each element in `items` to the queue.
@ -190,27 +194,16 @@ pub fn PriorityQueue(comptime T: type) type {
self.len = new_len;
}
fn linearSearch(elem: T, items: []const T) usize {
var found: usize = 0;
for (items) |item, i| {
if (item == elem) {
found = i;
break;
}
}
return found;
}
pub fn update(self: *Self, elem: T, new_elem: T) !void {
var update_index: usize = linearSearch(elem, self.items);
var update_index: usize = std.mem.indexOfScalar(T, self.items, elem) catch |error| return error.ElementNotFound;
assert (update_index >= 0 and update_index < self.items.len);
// Heapreplace:
// replace the item: self.items[update_index]= new_elem;
// swap the new item to the top of the heap: std.mem.swap(heap[0], heap[update_index]);
// sift up or down: which has been generically implemented as sift down: siftDown(self, 0)
const old_elem: T = self.items[update_index];
self.items[update_index] = new_elem;
std.mem.swap(T, &self.items[0], &self.items[update_index]);
siftDown(self, 0);
if (self.compareFn(new_elem, old_elem)) {
siftUp(self, update_index);
} else {
siftDown(self, update_index);
}
}
pub const Iterator = struct {