{"id":581,"date":"2024-10-19T13:53:13","date_gmt":"2024-10-19T08:23:13","guid":{"rendered":"https:\/\/codexplained.in\/?p=581"},"modified":"2025-11-24T15:32:48","modified_gmt":"2025-11-24T10:02:48","slug":"preorder-traversal-of-binary-tree","status":"publish","type":"post","link":"https:\/\/codexplained.in\/?p=581","title":{"rendered":"Preorder Traversal of Binary Tree"},"content":{"rendered":"
\n#include <stdio.h>\n#include <stdlib.h>\n\n\/\/ Define the structure of a tree node\nstruct Node {\n    int data;\n    struct Node* left;\n    struct Node* right;\n};\n\n\/\/ Function to create a new node\nstruct Node* createNode(int data) {\n    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));\n    newNode->data = data;\n    newNode->left = NULL;\n    newNode->right = NULL;\n    return newNode;\n}\n\n\/\/ Function for Preorder Traversal\nvoid preorderTraversal(struct Node* root) {\n    if (root == NULL) {\n        return;\n    }\n\n    \/\/ Visit the root node first\n    printf("%d ", root->data);\n\n    \/\/ Traverse the left subtree\n    preorderTraversal(root->left);\n\n    \/\/ Traverse the right subtree\n    preorderTraversal(root->right);\n}\n\nint main() {\n    \/\/ Manually creating the binary tree\n    struct Node* root = createNode(1);\n    root->left = createNode(2);\n    root->right = createNode(3);\n    root->left->left = createNode(4);\n    root->left->right = createNode(5);\n    root->right->right = createNode(6);\n\n    \/\/ Print Preorder Traversal\n    printf("Preorder Traversal of the binary tree is: ");\n    preorderTraversal(root);\n\n    return 0;\n}\n\n<\/pre><\/div>\n\n\n
Explanation: <\/strong><\/h3>\n\n\n\n
    \n
  1. Struct Definition<\/strong>:\n
      \n
    • struct Node<\/code> represents a node in the binary tree. Each node has data<\/code>, left<\/code>, and right<\/code>.<\/li>\n\n\n\n
    • The createNode<\/code> function allocates memory for a new node, assigns it the given data, and sets its left<\/code> and right<\/code> pointers to NULL<\/code>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Preorder Traversal Function<\/strong>:\n
        \n
      • preorderTraversal<\/code> is a recursive function that performs the preorder traversal.<\/li>\n\n\n\n
      • It first prints the data<\/code> of the current node.<\/li>\n\n\n\n
      • It then calls itself with root->left<\/code> to traverse the left subtree.<\/li>\n\n\n\n
      • After that, it calls itself with root->right<\/code> to traverse the right subtree.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
      • Building the Tree<\/strong>:\n
          \n
        • The main<\/code> function builds a binary tree by creating nodes and linking them as shown in the example.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
        • Output<\/strong>:\n
            \n
          • When preorderTraversal<\/code> is called with root<\/code>, it prints the values in preorder.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
            Output of the Program<\/strong><\/h3>\n\n\n\n
            When you run the program, the output will be:<\/p>\n\n\n\n
            Preorder Traversal of the binary tree is: 1 2 4 5 3 6\n<\/code><\/pre>\n\n\n\n
            How the Program Works<\/strong><\/h3>\n\n\n\n
              \n
            • The root node (1<\/code>) is visited first and printed.<\/li>\n\n\n\n
            • Then the left subtree of 1<\/code> (rooted at 2<\/code>) is traversed:\n
                \n
              • 2<\/code> is visited.<\/li>\n\n\n\n
              • Its left child 4<\/code> is visited.<\/li>\n\n\n\n
              • Its right child 5<\/code> is visited.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
              • After that, the right subtree of 1<\/code> (rooted at 3<\/code>) is traversed:\n
                  \n
                • 3<\/code> is visited.<\/li>\n\n\n\n
                • Its right child 6<\/code> is visited.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n
                  Thus, the traversal sequence is 1 2 4 5 3 6<\/code>.<\/p>\n