authorgravatar for bsvasan92@icloud.comBhargav Srinivasan <bsvasan92@icloud.com> 2020-09-22 03:46:13-07:00
committergravatar for bsvasan92@icloud.comBhargav Srinivasan <bsvasan92@icloud.com> 2020-09-22 03:46:13-07:00
log983830a4ae9955f95b46a4fb64d3914468226ccb
treea842d1d2b356abbf83d7ce60fb7bebadf22eced7
parenta5140cc9020f4e3649ccc14ca4317829ea289306

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

1 files changed, 13 insertions(+), 20 deletions(-)

lib/std/priority_queue.zig+13-20
...@@ -49,7 +49,12 @@ pub fn PriorityQueue(comptime T: type) type {...@@ -49,7 +49,12 @@ pub fn PriorityQueue(comptime T: type) type {
4949
50 fn addUnchecked(self: *Self, elem: T) void {50 fn addUnchecked(self: *Self, elem: T) void {
51 self.items[self.len] = elem;51 self.items[self.len] = elem;
52 var child_index = self.len;52 siftUp(self, self.len);
53 self.len += 1;
54 }
55
56 fn siftUp(self: *Self, start_index: usize) void {
57 var child_index = start_index;
53 while (child_index > 0) {58 while (child_index > 0) {
54 var parent_index = ((child_index - 1) >> 1);59 var parent_index = ((child_index - 1) >> 1);
55 const child = self.items[child_index];60 const child = self.items[child_index];
...@@ -61,7 +66,6 @@ pub fn PriorityQueue(comptime T: type) type {...@@ -61,7 +66,6 @@ pub fn PriorityQueue(comptime T: type) type {
61 self.items[child_index] = parent;66 self.items[child_index] = parent;
62 child_index = parent_index;67 child_index = parent_index;
63 }68 }
64 self.len += 1;
65 }69 }
6670
67 /// Add each element in `items` to the queue.71 /// Add each element in `items` to the queue.
...@@ -190,27 +194,16 @@ pub fn PriorityQueue(comptime T: type) type {...@@ -190,27 +194,16 @@ pub fn PriorityQueue(comptime T: type) type {
190 self.len = new_len;194 self.len = new_len;
191 }195 }
192196
193 fn linearSearch(elem: T, items: []const T) usize {
194 var found: usize = 0;
195 for (items) |item, i| {
196 if (item == elem) {
197 found = i;
198 break;
199 }
200 }
201 return found;
202 }
203
204 pub fn update(self: *Self, elem: T, new_elem: T) !void {197 pub fn update(self: *Self, elem: T, new_elem: T) !void {
205 var update_index: usize = linearSearch(elem, self.items);198 var update_index: usize = std.mem.indexOfScalar(T, self.items, elem) catch |error| return error.ElementNotFound;
206 assert (update_index >= 0 and update_index < self.items.len);199 assert (update_index >= 0 and update_index < self.items.len);
207 // Heapreplace:200 const old_elem: T = self.items[update_index];
208 // replace the item: self.items[update_index]= new_elem;
209 // swap the new item to the top of the heap: std.mem.swap(heap[0], heap[update_index]);
210 // sift up or down: which has been generically implemented as sift down: siftDown(self, 0)
211 self.items[update_index] = new_elem;201 self.items[update_index] = new_elem;
212 std.mem.swap(T, &self.items[0], &self.items[update_index]);202 if (self.compareFn(new_elem, old_elem)) {
213 siftDown(self, 0);203 siftUp(self, update_index);
204 } else {
205 siftDown(self, update_index);
206 }
214 }207 }
215208
216 pub const Iterator = struct {209 pub const Iterator = struct {