Data_structure/PostfixOperate.c at master · hwangyoungjin/Data_structure · GitHub

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#include <stdio.h>
#include <stdlib.h>

int stack[20];
int top = -1;

void push(int x);
int pop();

int main() {
	char exp[20];
	char* e;
	int n1, n2, n3, num;
	printf("Enter the expression :: ");
	scanf_s("%s", exp, sizeof(exp));
	e = exp;
	while (*e != '\0') {
		if (isdigit(*e)) { //Determine if character is numeric
			num = *e - 48;
			push(num);
		}
		else {
			n1 = pop();
			n2 = pop();
			switch (*e) {
			case '+':
				n3 = n1 + n2;
				break;
			case '-':
				n3 = n2 - n1;
				break;
			case '*':
				n3 = n2 * n1;
				break;
			case '/':
				n3 = n2 / n1;
				break;
			}
			push(n3);
		}
		e++; // address ++
	}
	printf("\nThe result of expression %s = %d\n\n", exp, pop());

	return 0;
}

void push(int x) {
	stack[++top] = x;
}

int pop() {
	return stack[top--];
}