C Data Structures and Algorithms
What is DSA?
DSA stands for Data Structures and Algorithms.
- A data structure is a way to store and organize data.
- An algorithm is a set of steps used to solve a problem.
Think of a kitchen:
- Data structures are like shelves and drawers. They help you organize things.
- Algorithms are like recipes. They tell you what to do, step by step.
In programming, data structures and algorithms work together. Data structures help you organize data, while algorithms help you work with it.
In this tutorial, you'll build your own ways to store and organize data, and learn how to work with it, one step at a time.
Data Structures and Algorithms
You already know one data structure: an array.
An array stores multiple values in a single variable, in a specific order.
The loop below is an algorithm. It finds the highest value in the array:
Example
Find the highest score:
#include <stdio.h>
int main() {
int scores[] = {72, 61, 95, 88};
int length = sizeof(scores) / sizeof(scores[0]);
int highest = scores[0];
for (int i = 1; i < length; i++) {
if (scores[i] > highest) {
highest = scores[i];
}
}
printf("Highest score: %d\n", highest);
return 0;
}Result:
Highest score: 95Here is how the algorithm works:
- Start with the first score as the highest.
- Check the next score. If it is higher, update the highest score.
- Repeat until all scores have been checked.
That's an algorithm: a set of steps to solve a problem. And you just used one!
Run the simulation below to see how the loop above works. Each column is one score in the array:
When you run the simulation, the yellow column is the one being compared. If it is bigger than the highest score so far, it becomes the new highest score (green), and the dashed line moves up.
Why Learn DSA?
- Faster programs - Learn how to make your code run faster and more efficiently.
- Better problem-solving - Learn how to choose the right solution for different problems.
- Job interviews - Many programming interviews include questions about data structures and algorithms.
- Understand how things work - Languages like Python and Java have ready-made data structures. By building them yourself in C, you learn how they work behind the scenes.
Why DSA in C?
Many programming languages have built-in data structures that are ready to use.
In C, you need to build many of them yourself, using things you already know:
- Structures (
struct) - to keep a value and a pointer together - Pointers - to connect one item to the next
malloc()andfree()- to create and remove items while the program runs
This takes a little more work. But it is also the best way to really understand how data structures work.
What You Will Learn
Each chapter introduces something new, with simple explanations and real-life examples to help you understand how it works.
| Chapter | The Idea | Real-Life Example |
|---|---|---|
| Searching | Find a value in your data | Finding a word in a dictionary |
| Sorting | Put values in order | Lining people up from shortest to tallest |
| Stacks | The last item in is the first item out | A stack of plates |
| Queues | The first item in is the first item out | People waiting in a line |
| Linked Lists | Items connected with pointers | Train cars hooked together |
| Trees | Items arranged in levels, like branches | Folders on a computer |
| Big O | Measure how fast an algorithm is | Counting steps instead of seconds |
Before You Start
The DSA chapters use these C topics. If one of them feels new, take a quick look back:
