Sort Colors

Sortingmedium

Course · Section 11: Working With Arrays · Lecture 172: Sorting Arrays

Given `arr` containing only `0`, `1`, and `2`, implement `sortColors(arr)` to sort it ascending in one pass (Dutch national flag). Return the array.

Input: sortColors([2,0,2,1,1,0])

Output: [0,0,1,1,2,2]

Input: sortColors([2,0,1])

Output: [0,1,2]

+ 1 hidden test run on Submit.

Common pitfalls

Advancing the mid pointer after swapping from the high side can skip an unprocessed value.

Approach & explanation (try first)

The Dutch national flag scan sorts three values in a single O(n) pass, O(1) space.

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