By Piyush Wairale (M.Tech, IIT Madras) · Former Instructor, IIT Madras BS Degree Programme · Mentor to 20,000+ GATE aspirants · Updated November 2026

GATE CSE 2027 Programming and Data Structures Syllabus (Official, IIT Madras)

Section 4 of the CS paper: Programming in C. Recursion. Arrays, stacks, queues, linked lists, trees, binary search trees, binary heaps, graphs.

See all sections in the GATE CS 2027 syllabus and exam pattern guide.

Topic-wise Weightage and Priority

Programming in C and Recursion

GATE C questions test semantics, not syntax. Master: pointer arithmetic (p + 1 moves by sizeof(*p) bytes), arrays vs pointers (a[i] ≡ *(a + i), and arrays decay to pointers when passed), static variables (initialised once, retain value across calls), call by value (C has no call by reference; you pass addresses), scope and lifetime, operator precedence (*p++ increments the pointer, (*p)++ increments the value), and string handling with the terminating ‘\0’.

For recursion, draw the recursion tree and count calls: for fun(n) = fun(n−1) + fun(n−2), the number of calls grows like Fibonacci. Know tail recursion and how activation records stack up on the call stack.

Arrays, Stacks, Queues and Linked Lists

Arrays: row-major address of A[i][j] = base + ((i − lb₁) × columns + (j − lb₂)) × element size. Stacks: infix to postfix conversion, postfix evaluation, recursion simulation; the number of valid stack permutations of n elements is the Catalan number C_n. Queues: in a circular queue of size n using the one-empty-slot convention, full is (rear + 1) mod n == front and capacity is n − 1. A queue can be built from two stacks. Linked lists: insertion/deletion code tracing, reversing a list, detecting a cycle (slow and fast pointers), and the O(1) vs O(n) costs at head and tail.

Trees and Binary Search Trees

A binary tree of height h (root at height 0) has at most 2^h+1 − 1 nodes. In any binary tree, leaves = nodes of degree 2 + 1. Number of structurally different binary trees with n nodes, and number of BSTs on n distinct keys, are both the Catalan number C_n = (2n)! / ((n+1)! n!). Inorder + preorder (or inorder + postorder) uniquely determines a binary tree; preorder + postorder alone does not (unless the tree is full). Inorder traversal of a BST gives sorted order. BST search, insert and delete are O(h): O(log n) when balanced, O(n) when skewed.

Binary Heaps

A binary heap is a complete binary tree stored in an array: for 1-based index i, children are at 2i and 2i+1, parent at ⌊i/2⌋. Insert and delete-min/max are O(log n); build-heap is O(n) (not O(n log n)); finding the max in a min-heap is O(n) and it lies among the leaves. Height of a heap with n nodes is ⌊log₂n⌋.

Graphs as Data Structures

An adjacency matrix uses O(V²) space with O(1) edge lookup; an adjacency list uses O(V + E) space and is better for sparse graphs. Traversal algorithms (BFS and DFS) are covered in the GATE CSE Algorithms guide.

Five GATE-Style Problems, Solved

Q1 (NAT). What does this print?

int a[] = {10, 20, 30, 40, 50};
int *p = a + 1;
printf("%d", *(p + 2) + p[-1]);

Solution: p points to 20. *(p + 2) = 40 and p[−1] = 10. Output: 50.

Q2 (NAT). For int fun(int n) { if (n <= 1) return 1; return fun(n−1) + fun(n−2); }, what is fun(5), and how many calls are made in total?
Solution: Values: fun(2)=2, fun(3)=3, fun(4)=5, fun(5)=8. Calls satisfy C(n) = 1 + C(n−1) + C(n−2) with C(0) = C(1) = 1, so C(5) = 15.

Q3 (NAT). Evaluate the postfix expression 6 2 3 + − 3 8 2 / + *.
Solution: 2+3=5, 6−5=1, 8/2=4, 3+4=7, 1×7 = 7.

Q4 (NAT). How many distinct BSTs can be formed with 4 distinct keys?
Solution: C₄ = 8!/(5! · 4!) = 14.

Q5 (NAT). What is the height of a binary heap with 100 nodes (root at height 0)?
Solution: ⌊log₂100⌋ = 6.

Common Mistakes to Avoid

Confusing *p++ with (*p)++ and misreading precedence.

Forgetting that static variables persist between recursive calls.

Assuming C passes arrays by value: changes inside the function affect the caller’s array.

Mixing up height conventions (root at height 0 vs 1) in tree formulas; read the question’s definition.

Saying build-heap is O(n log n): bottom-up heapify is O(n).

5-Week Preparation Strategy

Weeks 1 to 2: C programming: pointers, arrays, strings, storage classes, recursion. Trace 100+ small programs by hand. Week 3: Stacks, queues and linked lists. Week 4: Trees, BSTs and heaps, with counting formulas. Week 5: Solve 10 years of GATE CS PDS questions and take the Programming & DS tests in the GATE CSE 2027 Test Series. Continue with Algorithms next.

FAQs: GATE CSE 2027 Programming and Data Structures

GATE CSE 2027: All Subject-wise Guides

1. Engineering Mathematics · 2. Digital Logic · 3. Computer Organization & Architecture · 4. Programming & Data Structures · 5. Algorithms · 6. Theory of Computation · 7. Compiler Design · 8. Operating System · 9. Databases (DBMS) · 10. Computer Networks

Full paper overview: GATE CS 2027 Syllabus, Exam Pattern & Cutoff. Practise all ten subjects in one place with the GATE CSE 2027 Test Series.