Selection Sort Algorithm in DSA Javascript - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of selection sort on this array?

Given the array [29, 10, 14, 37, 13], what will be the array after the first two passes of selection sort?

DSA Javascript

const arr = [29, 10, 14, 37, 13];

// After first pass
// After second pass

// What is arr now?

A [10, 14, 13, 29, 37]

B [10, 13, 14, 29, 37]

C [10, 14, 13, 37, 29]

D [10, 13, 14, 37, 29]

💡 Hint

Selection sort picks the smallest element and swaps it with the current position.

First pass swaps 29 with 10: [10, 29, 14, 37, 13]. Second pass swaps 29 with 13: [10, 13, 14, 37, 29].

🧠 Conceptual

intermediate

How many swaps does selection sort perform on an array of length n?

Consider selection sort on an array of length n. How many swaps does it perform in the worst case?

A 0 swaps

B n swaps

C n*(n-1)/2 swaps

D n-1 swaps

💡 Hint

Selection sort swaps only once per pass after finding the minimum.

Selection sort performs exactly n-1 swaps because it swaps the smallest element into place once per pass.

❓ Predict Output

advanced

What is the final sorted array after running this selection sort code?

Given the code below, what is the final printed array?

DSA Javascript

function selectionSort(arr) {
  for (let i = 0; i < arr.length - 1; i++) {
    let minIndex = i;
    for (let j = i + 1; j < arr.length; j++) {
      if (arr[j] < arr[minIndex]) {
        minIndex = j;
      }
    }
    if (minIndex !== i) {
      [arr[i], arr[minIndex]] = [arr[minIndex], arr[i]];
    }
  }
  return arr;
}

const result = selectionSort([64, 25, 12, 22, 11]);
console.log(result);

A [11, 12, 22, 25, 64]

B [64, 25, 12, 22, 11]

C [11, 22, 12, 25, 64]

D [12, 11, 22, 25, 64]

💡 Hint

Selection sort sorts the array in ascending order by repeatedly selecting the smallest element.

The code correctly implements selection sort, resulting in the sorted array [11, 12, 22, 25, 64].

🔧 Debug

advanced

What error does this selection sort code produce?

Consider this code snippet. What error will it raise when run?

DSA Javascript

function selectionSort(arr) {
  for (let i = 0; i <= arr.length; i++) {
    let minIndex = i;
    for (let j = i + 1; j < arr.length; j++) {
      if (arr[j] < arr[minIndex]) {
        minIndex = j;
      }
    }
    [arr[i], arr[minIndex]] = [arr[minIndex], arr[i]];
  }
  return arr;
}

selectionSort([3, 1, 2]);

A TypeError: Cannot destructure property of undefined

B RangeError: Maximum call stack size exceeded

C TypeError: Cannot read property 'length' of undefined

D undefined is not a function

💡 Hint

Check the loop condition for i and how it affects array access.

The loop runs with i = arr.length, causing arr[i] to be undefined. Destructuring swap fails with TypeError.

🧠 Conceptual

expert

What is the time complexity of selection sort and why?

Select the correct time complexity of selection sort and the reason behind it.

A O(n) because it only swaps elements once per pass

B O(n log n) because it divides the array and merges sorted parts

C O(n^2) because it uses nested loops to find the minimum element for each position

D O(log n) because it uses binary search to find the minimum

💡 Hint

Think about how many comparisons selection sort makes in total.

Selection sort uses two nested loops, each running up to n times, resulting in O(n^2) time complexity.