initial commit

codes/core/heaps/binary_heap.py

@@ -0,0 +1,75 @@
+class BinHeap:
+    def __init__(self, nodes):
+        self.heap = []
+        self.pos = [-1] * nodes
+
+    def sift_up(self, idx):
+        heap = self.heap
+        pos = self.pos
+
+        backup = heap[idx]
+        cur = idx
+
+        while cur > 0:
+            par = (cur - 1) // 2
+            if backup[1] >= heap[par][1]:
+                break
+            heap[cur] = heap[par]
+            pos[heap[cur][0]] = cur
+            cur = par
+        heap[cur] = backup
+        pos[backup[0]] = cur
+
+    def sift_down(self, idx):
+        heap = self.heap
+        pos = self.pos
+        
+        n = len(heap)
+
+        backup = heap[idx]
+        cur = idx
+        
+        while True:
+            left = cur * 2 + 1
+            if left >= n:
+                break
+            right = left + 1
+            tar = right if right < n and heap[right][1] < heap[left][1] else left
+            if backup[1] <= heap[tar][1]:
+                break
+            heap[cur] = heap[tar]
+            pos[heap[cur][0]] = cur
+            cur = tar
+        heap[cur] = backup
+        pos[backup[0]] = cur
+        
+    def add(self, key, dist):
+        idx = len(self.heap)
+        self.heap.append([key, dist])
+        self.pos[key] = idx
+        self.sift_up(idx)
+    
+    def extract_min(self):
+        heap = self.heap
+        pos = self.pos
+        if not heap:
+            return None
+        min_node, min_dist = heap[0]
+        pos[min_node] = -1
+
+        last = heap.pop()
+        if heap:
+            heap[0] = last
+            pos[last[0]] = 0
+            self.sift_down(0)
+        return (min_node, min_dist)
+    
+    def decrease_key(self, key, new_dist):
+        idx = self.pos[key]
+        if idx == -1:
+            return None
+        node = self.heap[idx]
+        if new_dist >= node[1]:
+            return None
+        node[1] = new_dist
+        self.sift_up(idx)