GATE CS 2014 Set 3 — Question 52

MCQ+2 / -0.67MediumBinary Search & VariantsSearchingAlgorithmsControl FlowC ProgrammingProgramming & Data Structures

Algorithms → C Programming → Binary Search & Variants

Last updated 5 September 2026

Question

Consider the C function given below. Assume that the array listA contains n (> 0) elements, sorted in ascending order. int ProcessArray(int *listA, int x, int n) { int i, j, k; i = 0; j = n-1; do { k = (i+j)/2; if (x <= listA[k]) j = k-1; if (listA[k] <= x) i = k+1; }while (i <= j); if (listA[k] == x) return(k); else return -1; } Which one of the following statements about the function ProcessArray is CORRECT?

Correct answer (B) It is an implementation of binary search. Solution The function implements a variation of binary search . Trace: The loop continues as long as i <= j . k is the middle index. If x <= listA[k], the upper bound j is moved to k-1 . If listA[k] <= x, the lower bound i is moved to k+1 . If listA[k] == x : Both conditions are true. j becomes k-1 and i becomes k+1 . The loop condition i <= j becomes false (since k+1 > k-1), and the loop terminates. After the loop, listA[k] == x is checked. Since k holds the index where the match was found, it returns k . If x is not in the array: The range [i, j] shrinks until i > j without ever hitting the equality case simultaneously (or if it does, listA[k] won't be x unless x was found). The loop terminates, and the final check listA[k] == x fails, returning -1. Thus, it correctly searches for x in the sorted array listA . Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (B) It is an implementation of binary search. Solution The function implements a variation of binary search . Trace: The loop continues as long as i <= j . k is the middle index. If x <= listA[k], the upper bound j is moved to k-1 . If listA[k] <= x, the lower bound i is moved to k+1 . If listA[k] == x : Both conditions are true. j becomes k-1 and i becomes k+1 . The loop condition i <= j becomes false (since k+1 > k-1), and the loop terminates. After the loop, listA[k] == x is checked. Since k holds the index where the match was found, it returns k . If x is not in the array: The range [i, j] shrinks until i > j without ever hitting the equality case simultaneously (or if it does, listA[k] won't be x unless x was found). The loop terminates, and the final check listA[k] == x fails, returning -1. Thus, it correctly searches for x in the sorted array listA .

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