docs: Change variable names

Author: Panquesito7

data_structures/stack_using_linked_list.cpp

@@ -5,28 +5,28 @@ struct node {
     node *next;
 };
 
-node *top_var;
+node *stack_idx;
 
 void push(int x) {
     node *n = new node;
     n->val = x;
-    n->next = top_var;
-    top_var = n;
+    n->next = stack_idx;
+    stack_idx = n;
 }
 
 void pop() {
-    if (top_var == NULL) {
+    if (stack_idx == NULL) {
         std::cout << "\nUnderflow";
     } else {
-        node *t = top_var;
+        node *t = stack_idx;
         std::cout << "\n" << t->val << " deleted";
-        top_var = top_var->next;
+        stack_idx = stack_idx->next;
         delete t;
     }
 }
 
 void show() {
-    node *t = top_var;
+    node *t = stack_idx;
     while (t != NULL) {
         std::cout << t->val << "\n";
         t = t->next;

others/paranthesis_matching.cpp

@@ -20,13 +20,13 @@
 char stack[MAX];
 
 //! pointer to track stack index
-int top_var = -1;
+int stack_idx = -1;
 
 //! push byte to stack variable
-void push(char ch) { stack[++top_var] = ch; }
+void push(char ch) { stack[++stack_idx] = ch; }
 
 //! pop a byte out of stack variable
-char pop() { return stack[top_var--]; }
+char pop() { return stack[stack_idx--]; }
 
 //! @}-------------- end stack -----------
 
@@ -56,7 +56,7 @@ int main() {
     while (valid == 1 && i < exp.length()) {
         if (exp[i] == '(' || exp[i] == '{' || exp[i] == '[' || exp[i] == '<') {
             push(exp[i]);
-        } else if (top_var >= 0 && stack[top_var] == opening(exp[i])) {
+        } else if (stack_idx >= 0 && stack[stack_idx] == opening(exp[i])) {
             pop();
         } else {
             valid = 0;
@@ -65,7 +65,7 @@ int main() {
     }
 
     // makes sure the stack is empty after processsing (above)
-    if (valid == 1 && top_var == -1) {
+    if (valid == 1 && stack_idx == -1) {
         std::cout << "\nCorrect Expression";
     } else {
         std::cout << "\nWrong Expression";