From bad617ff79f931168876c56b656d08e1fc177188 Mon Sep 17 00:00:00 2001
From: ZakyHermawan <zaky.hermawan9615@gmail.com>
Date: Mon, 14 Jun 2021 10:44:46 +0700
Subject: [PATCH] Add postfix evaluation
---
evaluate_postfix.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 75 insertions(+)
create mode 100644 evaluate_postfix.c
diff --git a/evaluate_postfix.c b/evaluate_postfix.c
new file mode 100644
index 0000000..ee5e77e
--- /dev/null
+++ b/evaluate_postfix.c
@@ -0,0 +1,75 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct Node {
+ char data;
+ struct Node* before;
+} Node;
+
+Node* push(Node* node, char data) {
+ Node* new = (Node*)malloc(sizeof(Node));
+ new->data = data;
+ new->before = node;
+
+ return new;
+}
+
+Node* pop(Node* node) {
+ if(node == NULL) {
+ return node;
+ }
+ Node* ptr = node;
+ node = node->before;
+ free(ptr);
+ return node;
+}
+
+float eval(char a, char b, char operator) {
+ int operand1, operand2;
+ operand1 = ((int)a)-48;
+ operand2 = ((int)b)-48;
+
+ if(operator == '+') return operand1+operand2;
+ else if(operator == '-') return operand1-operand2;
+ else if(operator == '/') return operand1/operand2;
+ else if(operator == '*') return operand1*operand2;
+
+}
+
+int main() {
+ char exp[1000];
+ printf("Enter a postfix expression: ");
+ gets(exp);
+ puts(exp);
+ exp[strlen(exp)] = ')';
+ exp[strlen(exp)+1] = 0;
+ Node* stack = NULL;
+
+ float hasil = 0;
+
+ int idx = 0;
+ while(exp[idx] != ')') {
+ char now = exp[idx++];
+ if((int)now <= 57 && (int)now >=48) {
+ stack = push(stack, now);
+ }
+ else {
+ if(now == ' ') continue;
+ // now adalah oeprator
+ char a = stack->data;
+ stack = pop(stack);
+ char b = stack->data;
+ stack = pop(stack);
+ hasil = eval(b, a, now);
+ stack = push(stack, hasil+48);
+ }
+ }
+
+ printf("%.2f\n", hasil);
+
+
+
+
+ return 0;
+}
\ No newline at end of file
--
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