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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.lchild = None |
| 8 | + self.rchild = None |
| 9 | + |
| 10 | + |
| 11 | +class ExpressionTree: |
| 12 | + |
| 13 | + def __init__(self): |
| 14 | + self.root = None |
| 15 | + |
| 16 | + |
| 17 | + def buildTree(self, postfix): |
| 18 | + from queue import LifoQueue |
| 19 | + stack = LifoQueue() |
| 20 | + |
| 21 | + for i in range(len(postfix)): |
| 22 | + if isOperator( postfix[i] ): |
| 23 | + t = Node( postfix[i] ) |
| 24 | + t.rchild = stack.get() |
| 25 | + t.lchild = stack.get() |
| 26 | + stack.put(t) |
| 27 | + else: # operand |
| 28 | + t = Node(postfix[i]) |
| 29 | + stack.put(t) |
| 30 | + self.root = stack.get() |
| 31 | + |
| 32 | + |
| 33 | + def prefix(self): |
| 34 | + self._preorder(self.root) |
| 35 | + print() |
| 36 | + |
| 37 | + |
| 38 | + def _preorder(self, p): |
| 39 | + if p == None: |
| 40 | + return |
| 41 | + print(p.info, end = " ") |
| 42 | + self._preorder(p.lchild) |
| 43 | + self._preorder(p.rchild) |
| 44 | + |
| 45 | + |
| 46 | + def postfix(self): |
| 47 | + self._postorder(self.root) |
| 48 | + print() |
| 49 | + |
| 50 | + |
| 51 | + def _postorder(self,p): |
| 52 | + if p == None: |
| 53 | + return |
| 54 | + self._postorder(p.lchild) |
| 55 | + self._postorder(p.rchild) |
| 56 | + print(p.info, end = " ") |
| 57 | + |
| 58 | + |
| 59 | + def parenthesizedInfix(self): |
| 60 | + self._inorder(self.root) |
| 61 | + print() |
| 62 | + |
| 63 | + |
| 64 | + def _inorder(self, p): |
| 65 | + if p == None: |
| 66 | + return |
| 67 | + |
| 68 | + if isOperator(p.info): |
| 69 | + print("(", end = "") |
| 70 | + |
| 71 | + self._inorder(p.lchild) |
| 72 | + print(p.info, end = " ") |
| 73 | + self._inorder(p.rchild) |
| 74 | + |
| 75 | + if isOperator(p.info): |
| 76 | + print(")",end = "") |
| 77 | + |
| 78 | + |
| 79 | + def display(self): |
| 80 | + self._display(self.root,0) |
| 81 | + print() |
| 82 | + |
| 83 | + |
| 84 | + def _display(self,p,level): |
| 85 | + if p is None: |
| 86 | + return |
| 87 | + self._display(p.rchild, level+1) |
| 88 | + print() |
| 89 | + |
| 90 | + for i in range(level): |
| 91 | + print(" ", end='') |
| 92 | + print(p.info) |
| 93 | + self._display(p.lchild, level+1) |
| 94 | + |
| 95 | + |
| 96 | + def evaluate(self): |
| 97 | + if self.root == None: |
| 98 | + return 0 |
| 99 | + else: |
| 100 | + return self._evaluate(self.root) |
| 101 | + |
| 102 | + |
| 103 | + def _evaluate(self, p): |
| 104 | + if not isOperator(p.info) : |
| 105 | + return ord(p.info)-48 |
| 106 | + |
| 107 | + leftValue = self._evaluate(p.lchild) |
| 108 | + rightValue = self._evaluate(p.rchild) |
| 109 | + |
| 110 | + if p.info=='+': |
| 111 | + return leftValue + rightValue |
| 112 | + elif p.info=='-': |
| 113 | + return leftValue - rightValue |
| 114 | + elif p.info=='*': |
| 115 | + return leftValue * rightValue |
| 116 | + else: |
| 117 | + return leftValue // rightValue |
| 118 | + |
| 119 | + |
| 120 | +def isOperator(c): |
| 121 | + if c == '+' or c == '-' or c == '*' or c == '/' or c == '^': |
| 122 | + return True |
| 123 | + return False |
| 124 | + |
| 125 | +############################################################################################## |
| 126 | +if __name__ == '__main__': |
| 127 | + |
| 128 | + tree = ExpressionTree() |
| 129 | + |
| 130 | + postfix = "54+12*3*-" |
| 131 | + |
| 132 | + tree.buildTree(postfix) |
| 133 | + tree.display() |
| 134 | + |
| 135 | + print("Prefix : ") |
| 136 | + tree.prefix() |
| 137 | + |
| 138 | + print("Postfix : ") |
| 139 | + tree.postfix() |
| 140 | + |
| 141 | + print("Infix : ") |
| 142 | + tree.parenthesizedInfix() |
| 143 | + |
| 144 | + print("Value : " , tree.evaluate() ) |
| 145 | + |
| 146 | + |
| 147 | + |
| 148 | + |
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