From 27a602d8d2ca2494e8abfa19813f140a569ea93b Mon Sep 17 00:00:00 2001
From: Krishna Pradeep Dawalkar <krishna3dawalkar@gmail.com>
Date: Sun, 18 Oct 2020 22:21:12 +0530
Subject: [PATCH] Added Infix To Postfix Expression Converison using arrays

---
 STACKS/infixToPostfix_using_stacks.cpp | 160 +++++++++++++++++++++++++
 1 file changed, 160 insertions(+)
 create mode 100644 STACKS/infixToPostfix_using_stacks.cpp

diff --git a/STACKS/infixToPostfix_using_stacks.cpp b/STACKS/infixToPostfix_using_stacks.cpp
new file mode 100644
index 0000000..eea4144
--- /dev/null
+++ b/STACKS/infixToPostfix_using_stacks.cpp
@@ -0,0 +1,160 @@
+
+#include <iostream>
+#include <ctype.h>
+#include <string.h>
+using namespace std;
+ class Stack{
+typedef struct Node{
+    int data;
+    Node *next;
+}Node;
+
+  Node *top;
+ public:
+  Stack(){
+      top=NULL;
+  }
+   int isEmpty();
+
+    void push(int x);
+    int pop();
+    int Top();
+
+};
+int Stack::Top(){
+    return top->data;
+}
+int Stack::isEmpty(){
+    if (top==NULL){
+        return 1;
+    }else{
+    return 0;
+}}
+void Stack ::push(int b ){
+  Node *newNode;
+  newNode = new Node;
+  newNode->data=b;
+  newNode->next=top;
+  top=newNode;
+
+}
+int Stack ::pop( ){
+
+     int y;
+     Node *temp;
+     temp=top;
+     top=top->next;
+     y=temp->data;
+
+    delete temp;
+    return y;
+
+}
+
+int priority(char ch){
+ if(ch == '('|| ch==')'){
+     return 0;
+ }
+ if(ch=='+'|| ch=='-'){
+     return 1;
+ }
+ else if(ch=='*'|| ch=='/'){
+     return 2;
+ }else if(ch=='^'){
+     return 3;
+ }else{
+     return 4;
+ }
+}
+void infixToPostfix(char infix[20] ){
+    char x,tok; int i,j=0;
+    Stack s;
+    char post[20];
+    for(i=0;infix[i]!='\0';i++){
+        tok=infix[i];
+
+        if(isalnum(tok)){
+            post[j++]=tok;
+        }
+        else{
+            if(tok=='('){
+                s.push(tok);
+            }
+            else{
+                if(tok==')'){
+                while((x=s.pop())!='('){
+                    post[j++]=x;
+                }
+                }
+                else{
+                while(!s.isEmpty()&& priority(tok)<=priority(s.Top())){
+                    post[j++]=s.pop();
+                }
+                s.push(tok);
+            }
+
+        }
+    }
+    }
+        while(!s.isEmpty()){
+            post[j++]=s.pop();
+        }
+        post[j]='\0';
+        cout<<"\nPostfix form is:  ";
+        cout<<post;
+
+    }
+
+void infixToPrefix(char infix[20] ){
+    char x,tok; int i,j=0;
+    Stack s;
+    char pre[20];
+    for(i=strlen(infix)-1;i>=0;i--){
+        tok=infix[i];
+
+        if(isalnum(tok)){
+            pre[j++]=tok;
+        }
+        else{
+            if(tok==')'){
+                s.push(tok);
+            }
+            else{
+                if(tok=='('){
+                while((x=s.pop())!=')'){
+                    pre[j++]=x;
+                }
+                }
+                else{
+                while(!s.isEmpty()&& priority(tok)<priority(s.Top())){
+                    pre[j++]=s.pop();
+                }
+                s.push(tok);
+            }
+
+        }
+    }
+    }
+        while(!s.isEmpty()){
+            pre[j++]=s.pop();
+        }
+        pre[j]='\0';
+        cout<<"\nPrefix form is:  ";
+        for(i=strlen(infix)-1;i>=0;i--){
+            cout<<pre[i];
+        }
+        cout<<'\0';
+    }
+
+
+int main()
+{
+    char inf[20];
+    cout<<"enter infix form "<<endl;
+    cin>>inf;
+    infixToPostfix(inf);
+    infixToPrefix(inf);
+return 0;
+}
+
+