DSA · Theory

Selection Sort Algorithm

Theory

50/810

Selection Sort Algorithm

Selection Sort Algorithm is a DSA topic. In plain words you use it for names A→Z in the roll list. Don’t start with a slogan — start with that picture.

Smallest example: n log n vs n². Type it, run it, and say what you see. If you can do that from memory, you know Selection Sort Algorithm.

From the example next to this theory: Selection Sort Algorithm — selection sort repeatedly picks the minimum of the unsorted suffix.

Trap — unstable sort when equal keys matter. Fix that before you talk about advanced DSA.

Viva — what is Selection Sort Algorithm? Then show n log n vs n². Then name the trap.

Exam tip

What is Selection Sort Algorithm? Show this: n log n vs n². Trap: unstable sort when equal keys matter.

Example

def selection_sort(arr):
    a = arr[:]
    for i in range(len(a)):
        m = i
        for j in range(i + 1, len(a)):
            if a[j] < a[m]:
                m = j
        a[i], a[m] = a[m], a[i]
    return a

print(selection_sort([5, 1, 4, 2]))

Selection Sort Algorithm — selection sort repeatedly picks the minimum of the unsorted suffix.

Short notes

DefSelection Sort Algorithm — names A→Z in the roll list.
Rulen log n vs n²
Trapunstable sort when equal keys matter
Usethe roll list

DSA · Theory

Selection Sort Algorithm

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Theory

50/810

Selection Sort Algorithm

Selection Sort Algorithm is a DSA topic. In plain words you use it for names A→Z in the roll list. Don’t start with a slogan — start with that picture.

Smallest example: n log n vs n². Type it, run it, and say what you see. If you can do that from memory, you know Selection Sort Algorithm.

From the example next to this theory: Selection Sort Algorithm — selection sort repeatedly picks the minimum of the unsorted suffix.

Trap — unstable sort when equal keys matter. Fix that before you talk about advanced DSA.

Viva — what is Selection Sort Algorithm? Then show n log n vs n². Then name the trap.

Exam tip

What is Selection Sort Algorithm? Show this: n log n vs n². Trap: unstable sort when equal keys matter.

Example

def selection_sort(arr):
    a = arr[:]
    for i in range(len(a)):
        m = i
        for j in range(i + 1, len(a)):
            if a[j] < a[m]:
                m = j
        a[i], a[m] = a[m], a[i]
    return a

print(selection_sort([5, 1, 4, 2]))

Selection Sort Algorithm — selection sort repeatedly picks the minimum of the unsorted suffix.

Short notes

DefSelection Sort Algorithm — names A→Z in the roll list.
Rulen log n vs n²
Trapunstable sort when equal keys matter
Usethe roll list

Selection Sort Algorithm

Example

Short notes

Questions

Selection Sort Algorithm

Example

Short notes

Questions