TWO POINTERS
WHAT IS THE TWO POINTER TECHNIQUE?
WHAT IS THE TWO POINTER TECHNIQUE?
The two pointers technique is an algorithmic strategy where two pointers are used to traverse a data structure (usually an array or a list) in order to solve problems more efficiently.
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WHAT IS THE TWO POINTER TECHNIQUE?
Imagine you have a long row of textbooks lined up on the floor, and you want to find two textbooks that together are the heaviest. Instead of picking up every textbook and checking with every other textbook (which takes a long time, Nested loop), you and your friend start from opposite ends of the line. You move toward the middle, each picking up a textbook as you go, and checking if their combined weight is what you want.
WHAT IS THE TWO POINTER TECHNIQUE?
THE TWO POINTER TECHNIQUE IS NOT ONLY FOR SORTED ARRAYS !!!!!
Though sorted arrays would be the best use case, it is not limited to it
UNSORTED ARRAYS
LINKED LISTS
STRINGS
AND OTHERS...
The key idea behind the two-pointer technique is to maintain two pointers that move through the data structure, often in opposite directions, to solve a specific problem.
COMMON PATTERNS:
Opposite End Pointers
Same Direction Pointers
Fixed distance Pointers
Opposite End Pointers
One pointer starts at one end, and the second pointer on the other end
Same Direction Pointers
Both pointers start on the same direction with one delayed or lagging behind
Fixed distance Pointers
Referring to sliding window (we would look deeply later on)
TIME COMPLEXITY
O(n)
SPACE COMPLEXITY
O(1)
The two pointers themselves are typically stored in variables, which occupy a constant amount of memory regardless of the input size.
WHEN DO WE USE THIS TECHNIQUE
PAIR SEARCHING
OPPOSITE END PROCESSING
REARRANGING OR PARTITIONING
Many More...
Further Reading and Relevant Links
Team Algo Daily (Video)
Team Algo Daily (Website)
You know the drill, Let's go solve those Leetcode challenges
Thank you !!!!
S.I.T: DSA - Two Pointers
By Chineletam Ugwuadu (Letam)
