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Evaluation of Expression Tree in C++
In this problem, we are given an expression tree that consist of binary operations like +, - , /, *. We need to do the evaluation of the expression tree and then return the result.
Expression Tree is a special type of binary tree in which each node either consist of an operator or operand which are distributed as−
- Leaf nodes of the tree are values on which the operation is to be performed.
- Non-leaf nodes consist of the binary operator denoting the operation to be performed.
Let’s take an example to understand the problem,
Input:
Output: 1
Explanation:
Decoding the expression tree,
Exp = ( (5+9) / (2*7) )
= ( 14 / 14 )
= 1
Solution Approach:
A simple solution to the problem is by performing one operation each from root, for operends we will solve the subtree. As all operations are binary the nodes of a tree either have two childrens or none.
We will use recursion to solve each node's binary operation.
Program to illustrate the working of our solution,
Example
#include <bits/stdc++.h>
using namespace std;
class node {
public:
string value;
node *left = NULL, *right = NULL;
node(string x)
{
value = x;
}
};
int solveExpressionTree(node* root) {
if (!root)
return 0;
if (!root->left && !root->right)
return stoi(root->value);
int leftSubTreeSol = solveExpressionTree(root->left);
int rightSubTreeSol = solveExpressionTree(root->right);
if (root->value == "+")
return leftSubTreeSol + rightSubTreeSol;
if (root->value == "-")
return leftSubTreeSol - rightSubTreeSol;
if (root->value == "*")
return leftSubTreeSol * rightSubTreeSol;
if (root -> value == "/")
return leftSubTreeSol / rightSubTreeSol;
return -1;
}
int main()
{
node *root = new node("/");
root->left = new node("+");
root->left->left = new node("9");
root->left->right = new node("5");
root->right = new node("*");
root->right->left = new node("2");
root->right->right = new node("7");
cout<<"The evaluation of expression tree is "<<solveExpressionTree(root);
return 0;
}Output −
The evaluation of expression tree is 1
Updated on: 22-Jan-2021
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