Infix to Postfix conversion program implemented in C

C/infix_to_postfix.c

@@ -0,0 +1,97 @@
+/* Infix to Postfix Conversion */
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+void post(char inf[], char postfix[]);
+int pop();
+void push(int n);
+int arr[20];
+int top = -1, var[256];
+int main(void)
+{
+    char inf[20], postfix[20], c;
+    int val;
+    var['^'] = 5;
+    var['*'] = 3;
+    var['/'] = 3;
+    var['+'] = 2;
+    var['-'] = 2;
+    var['('] = 1;
+    printf("Enter the Infix expression\n");
+    scanf("%s", inf);
+    post(inf, postfix);
+    printf("Postfix Expression: %s\n", postfix);
+}
+int pop()
+{
+    top--;
+    return arr[top + 1];
+}
+void push(int n)
+{
+    top++;
+    arr[top] = n;
+}
+void post(char inf[], char postfix[])
+{
+    int i = 0, j = 0, k = strlen(inf);
+    push('(');
+    inf[k] = ')';
+    inf[k + 1] = '\0';
+    while (inf[i] != '\0')
+    {
+        if (inf[i] == '(')
+            push('(');
+        else if (inf[i] >= 'a' && inf[i] <= 'z')
+        {
+            postfix[j] = inf[i];
+            j++;
+        }
+        else if (inf[i] == '/' || inf[i] == '-' || inf[i] == '+' || inf[i] == '*' || inf[i] == '^')
+        {
+            if (arr[top] == '(')
+                push(inf[i]);
+            else
+            {
+                if (var[inf[i]] <= var[arr[top]])
+                {
+                    while (var[arr[top]] >= var[inf[i]])
+                    {
+                        postfix[j] = pop();
+                        j++;
+                    }
+                    push(inf[i]);
+                }
+                else
+                    push(inf[i]);
+            }
+        }
+        else if (inf[i] == ')')
+        {
+            while (arr[top] != '(')
+            {
+                postfix[j] = pop();
+                j++;
+            }
+            top--;
+        }
+        if (inf[i + 1] == '\0')
+            postfix[j] = '\0';
+        i++;
+    }
+}
+
+/* Test Cases
+
+a+b*(c^d-e)^(f+g*h)-i
+
+a*(b+c)/d
+
+Output:
+
+abcd^e-fgh*+^*+i-
+
+abc+*d/
+
+*/