GATE CS 2014 Set 3 — Question 51

MCQ+2 / -0.67MediumFunctions & RecursionC ProgrammingProgramming & Data StructuresTree TraversalsTrees

Programming & Data Structures → C Programming → Functions & Recursion

Last updated 5 September 2026

Question

Consider the pseudocode given below. The function DoSomething() takes as argument a pointer to the root of an arbitrary tree represented by the leftMostChild-rightSibling representation. Each node of the tree is of type treeNode . typedef struct treeNode* treeptr; struct treeNode { treeptr leftMostChild, rightSibling; }; int DoSomething (treeptr tree) { int value=0; if (tree != NULL) { if (tree->leftMostChild == NULL) value = 1; else value = DoSomething(tree->leftMostChild); value = value + DoSomething(tree->rightSibling); } return(value); } When the pointer to the root of a tree is passed as the argument to DoSomething, the value returned by the function corresponds to the

Correct answer (D) number of leaf nodes in the tree. Solution The function DoSomething traverses the tree using the Left-Child Right-Sibling representation. Let's analyze the logic: 1. If tree is NULL, it returns 0. 2. If tree->leftMostChild == NULL, it means the node has no children. In a general tree, a node with no children is a leaf . In this case, value is set to 1. 3. If tree->leftMostChild != NULL, it recursively calls DoSomething on the first child. This sums up the values from the children. 4. Finally, it adds DoSomething(tree->rightSibling) . This adds the result from the siblings. Essentially, for any node: If it is a leaf, it contributes 1 to the sum. If it is an internal node, it contributes the sum of the results of its children. The function also sums across all siblings. Therefore, the function counts the total number of leaf nodes in the tree (nodes with no children). Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (D) number of leaf nodes in the tree. Solution The function DoSomething traverses the tree using the Left-Child Right-Sibling representation. Let's analyze the logic: 1. If tree is NULL, it returns 0. 2. If tree->leftMostChild == NULL, it means the node has no children. In a general tree, a node with no children is a leaf . In this case, value is set to 1. 3. If tree->leftMostChild != NULL, it recursively calls DoSomething on the first child. This sums up the values from the children. 4. Finally, it adds DoSomething(tree->rightSibling) . This adds the result from the siblings. Essentially, for any node: If it is a leaf, it contributes 1 to the sum. If it is an internal node, it contributes the sum of the results of its children. The function also sums across all siblings. Therefore, the function counts the total number of leaf nodes in the tree (nodes with no children).

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