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evaluation of postfix expression

Azad Mahmud answered on July 22, 2023 Popularity 9/10 Helpfulness 1/10

answer evaluation of postfix expression

evaluation of postfix expression

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// C++ program to evaluate value of a postfix
// expression having multiple digit operands
#include <bits/stdc++.h>
using namespace std;
 
// The main function that returns value
// of a given postfix expression
int evaluatePostfix(char* exp)
{
    // Create a stack of capacity equal to expression size
    stack<int> st;
    int i;
 
    // Scan all characters one by one
    for (i = 0; exp[i]; ++i) {
         
        // If the character is blank space then continue
        if (exp[i] == ' ')
            continue;
 
        // If the scanned character is an
        // operand (number here),extract the full number
        // Push it to the stack.
        else if (isdigit(exp[i])) {
            int num = 0;
 
            // Extract full number
            while (isdigit(exp[i])) {
                num = num * 10 + (int)(exp[i] - '0');
                i++;
            }
            i--;
 
            // Push the element in the stack
            st.push(num);
        }
 
        // If the scanned character is an operator, pop two
        // elements from stack apply the operator
        else {
            int val1 = st.top();
            st.pop();
            int val2 = st.top();
            st.pop();
 
            switch (exp[i]) {
            case '+':
                st.push(val2 + val1);
                break;
            case '-':
                st.push(val2 - val1);
                break;
            case '*':
                st.push(val2 * val1);
                break;
            case '/':
                st.push(val2 / val1);
                break;
            }
        }
    }
    return st.top();
}
 
// Driver code
int main()
{
    char exp[] = "100 200 + 2 / 5 * 7 +";
   
    // Function call
    cout << evaluatePostfix(exp);
    return 0;
}
 
// This code is contributed by rathbhupendra

Popularity 9/10 Helpfulness 1/10 Language whatever

Source: www.geeksforgeeks.org

Tags: evaluation expression postfix whatever

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Contributed on Jul 22 2023

Azad Mahmud

0 Answers Avg Quality 2/10

evaluation of postfix expression

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