Below is a high-yield, pattern-driven set of two pointers problems. This covers all core concepts:

• opposite-direction pointers
• same-direction (fast/slow)
• partitioning
• deduplication
• linked list cycle detection
• in-place array manipulation

1. Opposite Direction (Sorted Arrays)

Core Skill

• One pointer left, one right
• Move based on condition

Problems

• Two Sum II - Input Array Is Sorted
• Valid Palindrome

Pattern

l, r = 0, len(nums) - 1
while l < r:
    if condition:
        l += 1
    else:
        r -= 1

Insight

• Works when array is sorted or symmetric