Sorting Algorithms

How Insertion Sort Works

  • Waiting
  • Being compared
  • Just moved
  • In final position
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Insertion sort, 12 values in random order.

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Starting order

Two to 48 numbers, used in the order you type them.

Insertion Sort

  1. 1for i in 1..n-1:
  2. 2 key = a[i]
  3. 3 j = i - 1
  4. 4 while j >= 0 and a[j] > key:
  5. 5 a[j+1] = a[j]
  6. 6 j -= 1
  7. 7 a[j+1] = key

How the Seven Compare

AlgorithmBestAverageWorstExtra memoryStable
BubbleO(n)O(n²)O(n²)O(1)Yes
InsertionO(n)O(n²)O(n²)O(1)Yes
SelectionO(n²)O(n²)O(n²)O(1)No
ShellO(n log n)O(n√n)O(n²)O(1)No
MergeO(n log n)O(n log n)O(n log n)O(n)Yes
QuickO(n log n)O(n log n)O(n²)O(log n)No
HeapO(n log n)O(n log n)O(n log n)O(1)No

Scroll the table sideways for the rest of the columns.

Stable means equal values keep their original order.