Added file stack using linkedlist

C/infix2post.c

@@ -0,0 +1,64 @@
+#include<stdio.h>
+
+#define size 100
+char arr[size];
+top= -1;
+
+void push(char x){
+    top++;
+    arr[top]=x;
+}
+void pop(){
+    if(arr[top]!='(')
+        printf("%c",arr[top]);
+    top--;
+}
+
+int pr(char c){
+    if(c=='+' || c=='-'){
+        return 1;
+    }
+    else if(c=='*' || c=='/' || c=='%'){
+        return 2;
+    }
+    else
+        return -1;
+}
+int isalnum(char c){
+    if((c>='a' && c<='z')||(c>='A' && c<='B')|| (c>='1' && c<='9'))
+        return 1;
+    else
+        return 0;    
+}
+int main(){
+
+    char a[size];
+    printf("exp:");
+    scanf("%s",a);
+    for(int i=0; a[i]!= '\0';i++){
+        if(isalnum(a[i])){
+            printf("%c",a[i]);
+        }
+        else{
+            if(top==-1 || a[i]=='(')
+                push(a[i]);
+            else if(a[i]==')'){
+                while(arr[top]!='('){
+                    pop();
+                }
+            }
+            else    {
+                while(pr(a[i])<=pr(arr[top]) && top>=0 && pr(a[i])!=-1){
+                    pop();
+                }
+                push(a[i]);
+            }
+        }
+    }
+    while (top>=0)
+    {
+        pop();
+    }
+
+    return 0;
+}

C/stackusingLL.c

@@ -0,0 +1,68 @@
+#include<stdio.h>
+#include<stdlib.h>
+
+struct node
+{
+    int data;
+    struct node * next;
+};
+struct node * top=NULL;
+
+void push(int x){
+    struct node *newnode;
+    newnode=(struct node *)malloc(sizeof(struct node));
+    newnode->next=NULL;
+    newnode->data=x;
+
+    if(top==NULL){
+        top=newnode;
+    }
+    else{
+        newnode->next=top;
+        top=newnode;
+    }
+}
+
+void pop(){
+    struct node * current=top;
+    if(top!=NULL)
+    {
+        top=current->next;
+        free(current);
+    }
+    else   printf("no elements");
+}
+
+void display(){
+    struct node * current=top;
+    while(current!=NULL){
+        printf("%d ",current->data);
+        current=current->next;
+    }
+}
+
+void main(){
+    int option=0;
+    int d;
+    while(1){
+        printf("\n1.push\t2.pop\t3.show\t0.exit:");
+        scanf("%d",&option);
+        switch (option)
+        {
+        case 1:
+            printf("data:");scanf("%d",&d);
+            push(d);
+            break;
+        case 2:
+            pop();
+            break;
+        case 3:
+            display();
+            break;   
+        case 0:
+            exit(0);     
+        default:
+            break;
+        }
+    }
+}