From b7da66c4280f6ce8dfac4694015fec82067bc4c2 Mon Sep 17 00:00:00 2001
From: akshat <jitikhatri@gmail.com>
Date: Sun, 1 Oct 2023 11:33:35 +0530
Subject: [PATCH] added a new algorithm to convert infix to postfix by using
 stack data structure

---
 .../stack/infix_to_postfix_using stacks.c     | 157 ++++++++++++++++++
 1 file changed, 157 insertions(+)
 create mode 100644 data_structures/stack/infix_to_postfix_using stacks.c

diff --git a/data_structures/stack/infix_to_postfix_using stacks.c b/data_structures/stack/infix_to_postfix_using stacks.c
new file mode 100644
index 00000000..b2c411b2
--- /dev/null
+++ b/data_structures/stack/infix_to_postfix_using stacks.c	
@@ -0,0 +1,157 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// Define the stack structure
+struct stack
+{
+    int size;  // Size of the stack
+    int top;   // Index of the top element
+    char *arr; // Array to store elements
+};
+
+// Function to get the top element of the stack
+char stackTop(struct stack *sp)
+{
+    return sp->arr[sp->top];
+}
+
+// Function to check if the stack is empty
+int isEmpty(struct stack *ptr)
+{
+    if (ptr->top == -1)
+    {
+        return 1; // True, stack is empty
+    }
+    else
+    {
+        return 0; // False, stack is not empty
+    }
+}
+
+// Function to check if the stack is full
+int isFull(struct stack *ptr)
+{
+    if (ptr->top == ptr->size - 1)
+    {
+        return 1; // True, stack is full
+    }
+    else
+    {
+        return 0; // False, stack is not full
+    }
+}
+
+// Function to push an element onto the stack
+void push(struct stack *ptr, char val)
+{
+    if (isFull(ptr))
+    {
+        printf("Stack Overflow! Cannot push %d to the stack\n", val);
+    }
+    else
+    {
+        ptr->top++;
+        ptr->arr[ptr->top] = val;
+    }
+}
+
+// Function to pop an element from the stack
+char pop(struct stack *ptr)
+{
+    if (isEmpty(ptr))
+    {
+        printf("Stack Underflow! Cannot pop from the stack\n");
+        return -1;
+    }
+    else
+    {
+        char val = ptr->arr[ptr->top];
+        ptr->top--;
+        return val;
+    }
+}
+
+// Function to determine the precedence of an operator
+int precedence(char ch)
+{
+    if (ch == '*' || ch == '/')
+        return 3;
+    else if (ch == '+' || ch == '-')
+        return 2;
+    else
+        return 0;
+}
+
+// Function to check if a character is an operator
+int isOperator(char ch)
+{
+    if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
+        return 1;
+    else
+        return 0;
+}
+
+// Function to convert infix expression to postfix
+char *infixToPostfix(char *infix)
+{
+    // Create a stack
+    struct stack *sp = (struct stack *)malloc(sizeof(struct stack));
+    sp->size = 10;
+    sp->top = -1;
+    sp->arr = (char *)malloc(sp->size * sizeof(char));
+
+    // Allocate memory for the postfix expression
+    char *postfix = (char *)malloc((strlen(infix) + 1) * sizeof(char));
+
+    int i = 0; // Track infix traversal
+    int j = 0; // Track postfix addition
+
+    // Process each character in the infix expression
+    while (infix[i] != '\0')
+    {
+        if (!isOperator(infix[i]))
+        {
+            // If it's not an operator, add it to the postfix expression
+            postfix[j] = infix[i];
+            j++;
+            i++;
+        }
+        else
+        {
+            // If it's an operator, handle it based on precedence
+            if (precedence(infix[i]) > precedence(stackTop(sp)))
+            {
+                push(sp, infix[i]);
+                i++;
+            }
+            else
+            {
+                postfix[j] = pop(sp);
+                j++;
+            }
+        }
+    }
+
+    // Pop remaining elements from the stack
+    while (!isEmpty(sp))
+    {
+        postfix[j] = pop(sp);
+        j++;
+    }
+
+    postfix[j] = '\0'; // Null-terminate the postfix expression
+    return postfix;
+}
+
+// Main function
+int main()
+{
+    // Infix expression
+    char *infix = "x-y/z-k*d";
+
+    // Convert infix to postfix and print the result
+    printf("Postfix is %s", infixToPostfix(infix));
+
+    return 0;
+}