Expression Tree program

Expression Tree/ExpressionTree.c

@@ -0,0 +1,157 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+struct exptree
+{
+	char data;
+	struct exptree *left;
+	struct exptree *right;
+};
+
+struct exptree *getnode(char);
+struct exptree *createExpTree(char[]);
+int precedence(char);
+void preOrder(struct exptree*);
+void inOrder(struct exptree*);
+void postOrder(struct exptree*);
+
+int main()
+{
+	struct exptree *root;
+	char exp[20];
+	printf("Enter the Infix Expression: ");
+	scanf("%s", exp);
+	root = createExpTree(exp);
+	printf("PreOrder: ");
+	preOrder(root);
+	printf("\nInOrder: ");
+	inOrder(root);
+	printf("\nPostOrder: ");
+	postOrder(root);
+	return 0;
+}
+
+struct exptree *getnode(char ch)
+{
+	struct exptree *newnode = (struct exptree*)malloc(sizeof(struct exptree));
+	newnode ->left = NULL;
+	newnode -> right = NULL;
+	newnode -> data = ch;
+	return newnode;
+}
+
+int precedence(char ch)
+{
+	switch(ch)
+	{
+		case '^':
+			return 3;
+		case '/':
+		case '*':
+			return 2;
+		case '-':
+		case '+':
+			return 1;
+		default:
+			return 0;
+	}
+}
+
+void preOrder(struct exptree *root)
+{
+	if(root != NULL)
+	{
+		printf("%c ", root->data);
+		preOrder(root->left);
+		preOrder(root->right);
+	}
+}
+
+void inOrder(struct exptree *root)
+{
+	if(root!=NULL)
+	{
+		inOrder(root->left);
+		printf("%c ", root->data);
+		inOrder(root->right);
+	}
+}
+
+void postOrder(struct exptree *root)
+{
+	if(root != NULL)
+	{
+		postOrder(root->left);
+		postOrder(root->right);
+		printf("%c ", root->data);
+	}
+}
+
+struct exptree *createExpTree(char exp[20])
+{
+	struct exptree *operst[10], *treest[10];
+	int top1 = -1, top2 = -1;
+	struct exptree *temp, *t1, *t2, *t3;
+	char symbol;
+	int i;
+	for(i=0;i<strlen(exp);i++)
+	{
+		symbol = exp[i];
+		if(isalnum(symbol))
+		{
+			temp = getnode(symbol);
+			treest[++top2] = temp;
+		}
+		else
+		{
+			temp = getnode(symbol);
+			if(symbol == '(')
+			{
+				operst[++top1] = temp;
+			}
+			else if(top1 == -1 ||  precedence(operst[top1]->data< precedence(symbol)))
+			{
+				operst[++top1] = temp;
+			}
+			else if(symbol == ')')
+			{
+				while(operst[top1]->data != '(' && top1 != -1 && top2 != -1 && precedence(operst[top1]->data) >= precedence(symbol))
+				{
+					t3 = operst[top1--];
+					t1 = treest[top2--];
+					t2 = treest[top2--];
+					t3->right = t1;
+					t3->left = t2;
+					treest[++top2] = t3;
+				}
+				if(operst[top1]->data =='(')
+					top1--;
+			}
+			else
+			{
+				while(top1 != -1 && top2 != -1 && precedence(operst[top1]->data >= precedence(symbol)))
+				{
+					t3 = operst[top1--];
+					t1 = treest[top2--];
+					t2 = treest[top2--];
+					t3->right = t1;
+					t3->left = t2;
+					treest[++top2] = t3;
+				}
+				operst[++top1] = temp;
+			}
+		}
+	}
+	while(top1 != -1)
+	{
+		t3 = operst[top1--];
+		t1 = treest[top2--];
+		t2 = treest[top2--];
+		t3->right = t1;
+		t3->left = t2;
+		treest[++top2] = t3;
+	}
+	return treest[top2];
+}