completed Competitive-Coding-1

Find-Missing-Number-in-a-sorted-array.py

@@ -0,0 +1,15 @@
+# tc O(log n), sc O(1).
+start, end = 0, len(nums) - 1
+
+while start <= end:
+    mid = start + ((end - start) // 2)
+
+    # find missing numbers upto mid index
+    missing_nums = nums[mid] - nums[0] - mid
+    if missing_nums < k:
+        start = mid + 1
+    else:
+        end = mid - 1
+
+missing_nums_upto_end = nums[end] - nums[0] - end
+return nums[end] + (k - missing_nums_upto_end)

Min-Heap-Implementation-using-Array.py

@@ -0,0 +1,54 @@
+# tc O(log n), for insert, extract_min, heapify_up, heapify_down, O(1) for get_min, size, is_empty,
+# sc O(n).
+class MinHeap:
+    def __init__(self):
+        self.heap = []
+
+    def parent(self, idx):
+        return (idx-1) // 2
+
+    def left_child(self, idx):
+        return 2 * idx + 1
+
+    def right_child(self, idx):
+        return 2 * idx + 2
+
+    def insert(self, item):
+        self.heap.append(item)
+        self._heapify_up(len(self.heap)-1)
+
+    def extract_min(self):
+        if not self.heap:
+            return None
+        if len(self.heap) == 1:
+            return self.heap.pop()
+        self.heap[0] = self.heap.pop()
+        self._heapify_down(0)
+
+    def _heapify_up(self, idx):
+        while idx > 0 and self.heap[idx] < self.heap[self.parent(idx)]:
+            self.heap[idx], self.heap[self.parent(idx)] = self.heap[self.parent(idx)], self.heap[idx]
+            idx = self.parent(idx)
+
+    def _heapify_down(self,index):
+        smallest = index
+        left = self.left_child(index)
+        right = self.right_child(index)
+
+        if left < len(self.heap) and self.heap[left] < self.heap[smallest]:
+                smallest = left
+            if right < len(self.heap) and self.heap[right] < self.heap[smallest]:
+                smallest = right
+
+            if smallest != index:
+                self.heap[index], self.heap[smallest] = self.heap[smallest], self.heap[index]
+                self._heapify_down(smallest)
+
+    def get_min(self):
+        return self.heap[0] if self.heap else None
+
+    def size(self):
+        return len(self.heap)
+
+    def is_empty(self):
+        return not self.heap