← Pointer Manipulation

Micro-Drill #8 — Remove duplicates (sorted array)

Pointer Manipulation Target: 10s

Two-pointer write keeps unique elements in-place with O(1) space. Core array cleanup technique.

# Two-pointer write — keep unique in-place
w = 1
for r in range(1, len(a)):
    if a[r] != a[r - 1]:
        a[w] = a[r]
        w += 1
# a[:w] has unique elements

Type it from memory. Go.

Practice Problems

• 26. Remove Duplicates from Sorted Array
• 80. Remove Duplicates from Sorted Array II

Related Coding Drills

• Drill #126 — Remove Duplicates from Sorted Array Easy
• Drill #4 — Two sum (sorted array) Easy
• Drill #56 — Min in rotated sorted array Medium