What is the time complexity of dutch national flag?

Worst case O(n). Space complexity is O(1).

Dutch national flag

medium

Three pointers carve the array into four regions, and the loop shrinks the unknown one to nothing. The one line everyone gets wrong: on a 2, mid does not advance.

Worst O(n)Space O(1)

Loading the dutch national flag engine…

Where to go next

Quick sort

medium

Partition around a pivot, then recurse on both halves.

Two pointers

easy

One comparison eliminates a whole row of the brute force.

Counting sort

medium

Sorting with zero comparisons.