Evaluate Postfix

Lab C Advanced 30 points

Evaluate a postfix expression of single-digit numbers and + - * / (no spaces), e.g. 23*5+. Use an int stack. Print the result.

Input

One expression.

Output

The result (integer division).

Example

Input

23*5+

Output

Sample input available Sample output available

Editor

Hints

Digits are pushed; an operator pops two values (the second popped is the left operand).

Solution explanation

Postfix needs no parentheses or precedence rules - a stack evaluates it left to right.

Show solution

#include <stdio.h>

int main() {
    char e[100];
    int stack[100], top = 0;
    scanf("%s", e);
    for (int i = 0; e[i] != '\0'; i++) {
        char c = e[i];
        if (c >= '0' && c <= '9') {
            stack[top] = c - '0';
            top++;
        } else {
            int b = stack[top - 1];
            int a = stack[top - 2];
            top -= 2;
            int r;
            if (c == '+') r = a + b;
            else if (c == '-') r = a - b;
            else if (c == '*') r = a * b;
            else r = a / b;
            stack[top] = r;
            top++;
        }
    }
    printf("%d\n", stack[0]);
    return 0;
}

Output

Answer