Added Stackintree.c

Data Structures/Stack/Stackintree.c

@@ -0,0 +1,155 @@
+#include<stdio.h>
+#include<stdlib.h>
+#define bool int
+
+/* A binary tree tNode has data, pointer to left child
+   and a pointer to right child */
+struct tNode
+{
+   int data;
+   struct tNode* left;
+   struct tNode* right;
+};
+
+/* Structure of a stack node. Linked List implementation is used for
+   stack. A stack node contains a pointer to tree node and a pointer to
+   next stack node */
+struct sNode
+{
+  struct tNode *t;
+  struct sNode *next;
+};
+
+/* Stack related functions */
+void push(struct sNode** top_ref, struct tNode *t);
+struct tNode *pop(struct sNode** top_ref);
+bool isEmpty(struct sNode *top);
+
+/* Iterative function for inorder tree traversal */
+void inOrder(struct tNode *root)
+{
+  /* set current to root of binary tree */
+  struct tNode *current = root;
+  struct sNode *s = NULL;  /* Initialize stack s */
+  bool done = 0;
+
+  while (!done)
+  {
+    /* Reach the left most tNode of the current tNode */
+    if(current !=  NULL)
+    {
+      /* place pointer to a tree node on the stack before traversing
+        the node's left subtree */
+      push(&s, current);                                              
+      current = current->left; 
+    }
+
+    /* backtrack from the empty subtree and visit the tNode
+       at the top of the stack; however, if the stack is empty,
+      you are done */
+    else                                                             
+    {
+      if (!isEmpty(s))
+      {
+        current = pop(&s);
+        printf("%d ", current->data);
+
+        /* we have visited the node and its left subtree.
+          Now, it's right subtree's turn */
+        current = current->right;
+      }
+      else
+        done = 1;
+    }
+  } /* end of while */ 
+}    
+
+/* UTILITY FUNCTIONS */
+/* Function to push an item to sNode*/
+void push(struct sNode** top_ref, struct tNode *t)
+{
+  /* allocate tNode */
+  struct sNode* new_tNode =
+            (struct sNode*) malloc(sizeof(struct sNode));
+
+  if(new_tNode == NULL)
+  {
+     printf("Stack Overflow \n");
+     getchar();
+     exit(0);
+  }           
+
+  /* put in the data  */
+  new_tNode->t  = t;
+
+  /* link the old list off the new tNode */
+  new_tNode->next = (*top_ref);  
+
+  /* move the head to point to the new tNode */
+  (*top_ref)    = new_tNode;
+}
+
+/* The function returns true if stack is empty, otherwise false */
+bool isEmpty(struct sNode *top)
+{
+   return (top == NULL)? 1 : 0;
+}  
+
+/* Function to pop an item from stack*/
+struct tNode *pop(struct sNode** top_ref)
+{
+  struct tNode *res;
+  struct sNode *top;
+
+  /*If sNode is empty then error */
+  if(isEmpty(*top_ref))
+  {
+     printf("Stack Underflow \n");
+     getchar();
+     exit(0);
+  }
+  else
+  {
+     top = *top_ref;
+     res = top->t;
+     *top_ref = top->next;
+     free(top);
+     return res;
+  }
+}
+
+/* Helper function that allocates a new tNode with the
+   given data and NULL left and right pointers. */
+struct tNode* newtNode(int data)
+{
+  struct tNode* tNode = (struct tNode*)
+                       malloc(sizeof(struct tNode));
+  tNode->data = data;
+  tNode->left = NULL;
+  tNode->right = NULL;
+
+  return(tNode);
+}
+
+/* Driver program to test above functions*/
+int main()
+{
+
+  /* Constructed binary tree is
+            1
+          /   \
+        2      3
+      /  \
+    4     5
+  */
+  struct tNode *root = newtNode(1);
+  root->left        = newtNode(2);
+  root->right       = newtNode(3);
+  root->left->left  = newtNode(4);
+  root->left->right = newtNode(5);
+
+  inOrder(root);
+
+  getchar();
+  return 0;
+}