What Hello Algo is
Hello Algo is an open learning book about data structures and algorithms. It is beginner-friendly: lots of animations, visual explanations, smooth difficulty, and runnable code in many languages.
The project supports Chinese, English, Japanese, and Russian, with examples in Python, Java, C++, C, C#, JavaScript, Go, Swift, Rust, Ruby, Kotlin, TypeScript, and Dart. That helps readers focus on algorithm ideas rather than one language.
What is inside
The book moves from basic data structures to algorithms, complexity, sorting, trees, graphs, and practice problems. Visualization is central: recursion, swaps, tree traversal, and queue behavior become visible processes.
Learning-example shape
This shows the book style: one idea can be expressed in many languages.
def binary_search(nums, target):
left, right = 0, len(nums) - 1
while left <= right:
mid = (left + right) // 2
if nums[mid] == target:
return mid
if nums[mid] < target:
left = mid + 1
else:
right = mid - 1
return -1Why it is useful
Hello Algo is a good first structured path into algorithms. It lowers the entry barrier by placing visuals, explanation, and code together.
Limits
It is an introductory book, not a replacement for competitive-programming training or a university course. Hard problems still need practice, proofs, mistake review, and deeper material.