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Algorithms
Complexity Analysis
GATE 2017
Easy

Match the algorithms with their time complexities:

Algorithm: (P) Towers of Hanoi with n disks (Q) Binary search given n sorted numbers (R) Heap sort given n numbers at the worst case (S) Addition of two n × n matrices

Time complexity: (i) Θ(n²) (ii) Θ(n log n) (iii) Θ(2ⁿ) (iv) Θ(log n)

  • AP→(iii), Q→(iv), R→(i), S→(ii)
  • BP→(iv), Q→(iii), R→(i), S→(ii)
  • P→(iii), Q→(iv), R→(ii), S→(i)
  • DP→(iv), Q→(iii), R→(ii), S→(i)

Explanation

Towers of Hanoi with n disks requires 2ⁿ−1 moves → Θ(2ⁿ) = (iii). Binary search on n sorted elements → Θ(log n) = (iv). Heap sort's worst case is Θ(n log n) = (ii). Adding two n×n matrices touches every one of the n² entries once → Θ(n²) = (i). So P→iii, Q→iv, R→ii, S→i.

Source: GATE CS 2017 (Session 2) (2017)

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