add infix to postfix conversion

infixToPostfixConversion.c

+#include <stdio.h>
+#include <string.h>
+#include <stdlib.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;
+}
+
+Node* erase(Node* node) {
+    if(node == NULL) {
+        return NULL;
+    }
+    while(node->before != NULL) {
+        Node* ptr = node;
+        node = node->before;
+        free(ptr);
+    }
+
+    free(node);
+    node = NULL;
+    return node;
+}
+
+int precedence(char c) {
+    if(c == '+' || c == '-') return 1;
+    else if(c == '*' || c == '/' || c == '%') return 2;
+    else return 0;
+}
+
+int main() {
+    char exp[1000];
+    char hasil[1000];
+    for(int i=0; i<1000; ++i) hasil[i] = 0;
+    printf("Enter an expression: ");
+    scanf("%s", exp);
+    size_t len = strlen(exp);
+    exp[len] = ')';
+    exp[len+1] = 0;
+    int idx = 0;
+    int i_hasil = 0;
+    Node* stack = NULL;
+    stack = push(stack, '(');
+
+    while(idx != len+1) {
+        char now = exp[idx++];
+        printf("%s\n", hasil);
+        if(now == '(') {
+            stack = push(stack, now);
+        }
+        else if(now == '+' || now == '-' || now == '*' || now == '/' || now == '%') {
+            while(1) {
+                int now_pres = precedence(now);
+                int stack_pres = precedence(stack->data);
+                if(stack_pres >= now_pres) {
+                    hasil[i_hasil++] = stack->data;
+                    stack = pop(stack);
+                }
+                else {
+                    
+                    stack = push(stack, now);
+                    break;
+                }
+            }
+            
+        }
+        else if(now == ')') {
+            char operator = stack->data;
+            while(operator != '(') {
+                hasil[i_hasil++] = operator;
+                stack = pop(stack);
+                operator = stack->data;
+            }
+            stack = pop(stack);
+        }
+        else {
+            hasil[i_hasil++] = now;
+        }
+    }
+    while(stack != NULL) {
+        char now = stack->data;
+        if(now == '(') break;
+        hasil[i_hasil++] = stack->data;
+        stack = pop(stack);
+    }
+    printf("%s\n", hasil);
+}
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