Update Paranthesis Matching.cpp

Others/Paranthesis Matching.cpp

@@ -1,52 +1,63 @@
 #include<iostream>
-#include<stdlib.h>
 #include<string>
-#include<stdio.h>
+
 using namespace std;
 
-const int MAX = 100;
+#define MAX 100
 
 // -------------- stack --------------
 
 char stack[MAX];
-int top=0;
+int top = -1;
 
-void push(char ch)
-{
-	stack[top++]=ch;
+void push(char ch){
+	stack[ ++top ] = ch;
 }
 
-char pop()
-{
-	return stack[--top];
+char pop(){
+	return stack[ top-- ];
 }
 
 // -------------- end stack -----------
 
-int main()
-{
+char opening(char ch){
+	switch(ch){
+		case '}':
+			return '{';
+		case ']':
+			return '[';
+		case ')':
+			return '(';
+		case '>':
+			return '<';		
+	}
+}
+
+int main(){
+
 	string exp;
+	int valid = 1, i = 0;
 	cout<<"Enter The Expression : ";
 	cin >> exp;
-	for (int i = 0; i < exp.length(); i++)
-	{
-			if (exp[i]=='(' || exp[i]=='{' || exp[i]=='[' || exp[i]=='<')
-			{
+	
+	while (valid == 1 && i < exp.length()){
+			if (exp[i] == '(' || exp[i] == '{' || exp[i] == '[' || exp[i] == '<'){
 				push(exp[i]);
 			}
-			else if (exp[i]==')' || exp[i]=='}' || exp[i]==']' || exp[i]=='>')
-			{
-                pop();
+			else if (top >= 0 && stack[top] == opening(exp[i])){
+				pop();
 			}
+			else{
+				valid = 0;
+			}
+			i++;
 	}
 
     // makes sure the stack is empty after processsing (above)
-	if(top==0)
-	{
-		cout<<"Correct Expression";
+	if (valid == 1 && top == -1){
+		cout<<"\nCorrect Expression";
 	}
-	else
-	{
+	else{
 		cout<<"\nWrong Expression";
 	}