Added a code for merging K sorted arrays

code/unclassified/src/Merge_K_sorted/Merge.py

@@ -0,0 +1,97 @@
+
+import sys 
+from typing import List, Optional 
+Matrix = List[List[int]] 
+
+
+class MinHeapNode: 
+    def __init__(self, el, i, j): 
+        self.element = el
+        self.i = i
+        self.j = j         
+
+class MinHeap: 
+    def __init__(self, ar: List[MinHeapNode], size: int):
+        """
+
+        :type ar: object
+        """
+        self.heap_size = size 
+        self.heap_arr = ar 
+        i = (self.heap_size - 1) // 2
+        while i >= 0: 
+            self.__min_heapify__(i)
+            i -= 1
+
+
+    def __min_heapify__(self, i):
+        l = __left__(i) 
+        r = __right__(i) 
+        smallest = i 
+        if l < self.heap_size and self.heap_arr[l].element < self.heap_arr[i].element: 
+            smallest = l 
+        if r < self.heap_size and self.heap_arr[r].element < self.heap_arr[smallest].element: 
+            smallest = r 
+        if smallest != i: 
+            __swap__(self.heap_arr, i, smallest) 
+            self.__min_heapify__(smallest)
+
+    def __get_min__(self) -> Optional:
+        if self.heap_size <= 0: 
+            print('Heap underflow') 
+            return None
+        return self.heap_arr[0] 
+
+
+    def __replace_min__(self, root):
+        self.heap_arr[0] = root 
+        self.__min_heapify__(0)
+
+
+def __left__(i):
+    return 2 * i + 1
+
+
+def __right__(i):
+    return 2 * i + 2
+
+
+def __swap__(arr: List[MinHeapNode], i, j):
+    temp = arr[i] 
+    arr[i] = arr[j] 
+    arr[j] = temp 
+
+
+def __merge_k_sorted_arrays__(arr: Matrix, k: int):
+    # type: (object, object) -> object
+    h_arr = [] 
+    result_size = 0
+    for i in range(len(arr)): 
+        node = MinHeapNode(arr[i][0], i, 1) 
+        h_arr.append(node) 
+        result_size += len(arr[i]) 
+
+    min_heap = MinHeap(h_arr, k) 
+    result = [0]*result_size 
+    for i in range(result_size): 
+        root = min_heap.__get_min__()
+        result[i] = root.element 
+        if root.j < len(arr[root.i]): 
+            root.element = arr[root.i][root.j] 
+            root.j += 1
+        else: 
+            root.element = sys.maxsize 
+        min_heap.__replace_min__(root)
+    for x in result: 
+        print(x, end=' ') 
+    print() 
+
+
+if __name__ == '__main__': 
+    arr = [ 
+        [1, 2, 12, 20], 
+        [1, 10, 15, 1003], 
+        [23, 30, 45, 1500] 
+    ] 
+    print('Merged Array is:') 
+    __merge_k_sorted_arrays__(arr, len(arr))