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| 1 | +# Copyright (C) Deepali Srivastava - All Rights Reserved |
| 2 | +# This code is part of DSA course available on CourseGalaxy.com |
| 3 | + |
| 4 | +class Node: |
| 5 | + def __init__(self,value): |
| 6 | + self.info = value |
| 7 | + self.left = None |
| 8 | + self.right = None |
| 9 | + self.leftThread = True |
| 10 | + self.rightThread = True |
| 11 | + |
| 12 | + |
| 13 | +class ThreadedBinaryTree: |
| 14 | + |
| 15 | + def __init__(self): |
| 16 | + self.root = None |
| 17 | + |
| 18 | + |
| 19 | + def _inorderPredecessor(self, p): |
| 20 | + if p.leftThread == True: |
| 21 | + return p.left |
| 22 | + else: |
| 23 | + p = p.left |
| 24 | + while p.rightThread == False: |
| 25 | + p = p.right |
| 26 | + return p |
| 27 | + |
| 28 | + |
| 29 | + def _inorderSuccessor(self, p): |
| 30 | + if p.rightThread == True: |
| 31 | + return p.right |
| 32 | + else: |
| 33 | + p = p.right |
| 34 | + while p.leftThread == False: |
| 35 | + p = p.left |
| 36 | + return p |
| 37 | + |
| 38 | + |
| 39 | + def inorder(self): |
| 40 | + if self.root == None: |
| 41 | + print("Tree is empty") |
| 42 | + return |
| 43 | + |
| 44 | + #Find the leftmost node of the tree |
| 45 | + p = self.root |
| 46 | + while p.leftThread == False: |
| 47 | + p = p.left |
| 48 | + |
| 49 | + while p!=None: |
| 50 | + print(p.info, end = " ") |
| 51 | + if p.rightThread == True: |
| 52 | + p = p.right |
| 53 | + else: |
| 54 | + p = p.right |
| 55 | + while p.leftThread == False: |
| 56 | + p = p.left |
| 57 | + print() |
| 58 | + |
| 59 | + |
| 60 | + def insert(self, x): |
| 61 | + p = self.root |
| 62 | + par = None |
| 63 | + |
| 64 | + while p!=None : |
| 65 | + par = p |
| 66 | + if x < p.info: |
| 67 | + if p.leftThread == False: |
| 68 | + p = p.left |
| 69 | + else: |
| 70 | + break |
| 71 | + elif x > p.info: |
| 72 | + if p.rightThread == False: |
| 73 | + p = p.right |
| 74 | + else: |
| 75 | + break |
| 76 | + else: |
| 77 | + print(x , " already present in the tree") |
| 78 | + return |
| 79 | + |
| 80 | + temp = Node(x) |
| 81 | + if par == None: |
| 82 | + self.root = temp |
| 83 | + elif x < par.info: #inserted as left child |
| 84 | + temp.left = par.left |
| 85 | + temp.right = par |
| 86 | + par.leftThread = False |
| 87 | + par.left = temp |
| 88 | + else: #inserted as right child |
| 89 | + temp.left = par |
| 90 | + temp.right = par.right |
| 91 | + par.rightThread = False |
| 92 | + par.right = temp |
| 93 | + |
| 94 | + def delete(self, x): |
| 95 | + p = self.root |
| 96 | + par = None |
| 97 | + |
| 98 | + while p != None: |
| 99 | + if x == p.info: |
| 100 | + break |
| 101 | + par = p |
| 102 | + if x < p.info: |
| 103 | + if p.leftThread == False: |
| 104 | + p = p.left |
| 105 | + else: |
| 106 | + break |
| 107 | + else: |
| 108 | + if p.rightThread == False: |
| 109 | + p = p.right |
| 110 | + else: |
| 111 | + break |
| 112 | + |
| 113 | + if p == None or p.info != x: |
| 114 | + print(x , " not found") |
| 115 | + return |
| 116 | + |
| 117 | + |
| 118 | + if p.leftThread == False and p.rightThread == False: #Case C: 2 children |
| 119 | + #Find inorder successor and its parent |
| 120 | + ps = p |
| 121 | + s = p.right |
| 122 | + |
| 123 | + while s.leftThread == False: |
| 124 | + ps = s |
| 125 | + s = s.left |
| 126 | + |
| 127 | + p.info = s.info |
| 128 | + p = s |
| 129 | + par = ps |
| 130 | + |
| 131 | + |
| 132 | + #Case A : No child |
| 133 | + if p.leftThread == True and p.rightThread == True: |
| 134 | + if par == None: |
| 135 | + self.root = None |
| 136 | + elif p == par.left: |
| 137 | + par.leftThread = True |
| 138 | + par.left = p.left |
| 139 | + else: |
| 140 | + par.rightThread = True |
| 141 | + par.right = p.right |
| 142 | + return |
| 143 | + |
| 144 | + #Case B : 1 child |
| 145 | + if p.leftThread == False: #node to be deleted has left child |
| 146 | + ch = p.left |
| 147 | + else: #node to be deleted has right child |
| 148 | + ch = p.right |
| 149 | + |
| 150 | + if par == None: #node to be deleted is root node |
| 151 | + self.root = ch |
| 152 | + elif p == par.left: #node is left child of its parent |
| 153 | + par.left = ch |
| 154 | + else: #node is right child of its parent |
| 155 | + par.right = ch |
| 156 | + |
| 157 | + pred = self._inorderPredecessor(p) |
| 158 | + succ = self._inorderSuccessor(p) |
| 159 | + |
| 160 | + if p.leftThread == False: #if p has left child, right is a thread |
| 161 | + pred.right = succ |
| 162 | + else: #p has right child,left is a thread |
| 163 | + succ.left = pred |
| 164 | + |
| 165 | + |
| 166 | + |
| 167 | + |
| 168 | +############################################################################################## |
| 169 | + |
| 170 | + |
| 171 | +if __name__ == '__main__': |
| 172 | + |
| 173 | + tree = ThreadedBinaryTree() |
| 174 | + |
| 175 | + while True: |
| 176 | + print("1.Insert a new node") |
| 177 | + print("2.Delete a node") |
| 178 | + print("3.Inorder Traversal") |
| 179 | + print("4.Quit") |
| 180 | + choice = int(input("Enter your choice : ")) |
| 181 | + |
| 182 | + if choice == 1: |
| 183 | + x = int(input("Enter the key to be inserted : ")) |
| 184 | + tree.insert(x) |
| 185 | + elif choice == 2: |
| 186 | + x = int(input("Enter the element to be deleted : ")) |
| 187 | + tree.delete(x) |
| 188 | + elif choice == 3: |
| 189 | + tree.inorder() |
| 190 | + elif choice == 4: |
| 191 | + break |
| 192 | + else: |
| 193 | + print("Wrong choice") |
| 194 | + print() |
| 195 | + |
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