Merge pull request #446 from dexter006/master

Parenthesis balance

Author: amritansh22

parenthesis.cpp

@@ -0,0 +1,144 @@
+#include<stdio.h>
+#include<stdlib.h>
+#include<string>
+struct node
+{
+	int data;
+	struct node* next;
+}*top = NULL;
+void display()
+{
+	struct node* p;
+	p = top;
+	while (p != NULL)
+	{
+		printf("%d  ", p->data);
+		p = p->next;
+	}
+	printf("\n");
+}
+void push( int x)
+{
+	struct node* t;
+	t = (struct node*)malloc(sizeof(struct node));
+	if (t == NULL)
+		printf("stack is full\n");
+	else
+	{
+		t->data = x;
+		t->next = top;
+		top = t;
+	}
+}
+int pop()
+{
+	int x = -1;
+	struct node* t;
+	if (top == NULL)
+		printf("stack is empty\n");
+	else
+	{
+		t = top;
+		top = top ->next;
+		x = t->data;
+		free(t);
+	}
+	return x;
+}
+int isbalanced(const char* exp)
+{
+	for (int i = 0; exp[i] != '\0'; i++)
+	{
+		if (exp[i] == '(')
+		push(exp[i]);
+		else if (exp[i] == ')')
+		{
+			if (top == NULL)
+				return 0;
+			pop();
+		}
+	}
+	if (top == NULL)
+		return 1;
+	else
+		return 0;
+}
+int pre(char x)
+{
+	if (x == '+' || x == '-')
+		return 1;
+	else if(x=='*'||x== '/' )
+		return 2;
+	return 0;
+}
+int isoperand(char x)
+{
+	if (x == '+' || x == '-' || x == '*' || x == '/')
+		return 0;
+	else
+		return 1;
+}
+char* intopost(const char* infix)
+{
+	int i = 0, j = 0;
+	char* postfix;
+	int len = strlen(infix);
+	postfix = (char*)malloc((len + 1) * sizeof(char));
+	while (infix[i] != '\0')
+	{
+		if (isoperand(infix[i]))
+			postfix[j++] = infix[i++];
+		else
+		{
+			if (pre(infix[i]) > pre(top->data))
+				push(infix[i++]);
+			else
+				postfix[j++] = pop();
+		}
+	}
+	while (top != NULL)
+		postfix[j++] = pop();
+	postfix[j] = '\0';
+	return postfix;
+}
+int eval(const char* postfix)
+{
+	int x1, x2, r;
+	for (int i = 0; postfix[i] != '\0'; i++)
+	{
+		if (isoperand(postfix[i]))
+			push(postfix[i]-'0');
+		else
+		{
+			x2 = pop();
+			x1 = pop();
+			switch (postfix[i])
+			{
+			case '+':
+				r = x1 + x2;
+				break;
+			case '-':
+				r = x1 -x2;
+				break;
+			case '*':
+				r = x1 *x2;
+				break;
+			case '/':
+				r = x1 /x2;
+				break;
+			}
+			push (r);
+		}
+	}
+	return top->data;
+}
+int main()
+{
+	/*const char* infix = "a+b*c";
+	push('#');
+	char* postfix = intopost(infix);
+	printf("%s", postfix);*/
+	const char* postfix = "234*+82/-";
+	printf("%d",eval(postfix));
+	return 0;
+}