C/C++ Algorithms

Linear Search

Linear search checks each item until it finds a match or reaches the end.

What is Linear Search?

Linear search checks each item until it finds a match or reaches the end.

Find a target in unsorted data.

Important points

Test empty, single-element, duplicate, and already sorted inputs.
Separate correctness from optimization.
Use the standard library in production unless a custom implementation is justified.

Linear Search visualizer

O(n)

Use Play or Step to follow each comparison and data movement.

C and C++ code examples

Run code →

main.c

#include <stdio.h>

int find(const int *values, int size, int target) {
    for (int index = 0; index < size; ++index) {
        if (values[index] == target) return index;
    }
    return -1;
}

int main(void) {
    int values[] = {14, 3, 27, 8, 19};
    printf("index=%d\n", find(values, 5, 8));
}

Expected output

index=3

C++

Run code →

main.cpp

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
    std::vector values{14, 3, 27, 8, 19};
    auto match = std::find(values.begin(), values.end(), 8);
    std::cout << "index="
              << std::distance(values.begin(), match) << '\n';
}

Expected output

index=3

C and C++ comparison

Both implementations run in O(n) worst-case time. C returns a signed index so -1 can mean not found; C++ returns an iterator and compares it with end.

Loops, pointers, lengths, and temporary buffers are written explicitly.

C++

Iterators and standard algorithms separate operations from container representation.

Practice exercises

Run both versions, then modify them to observe the different language guarantees.

Trace each comparison on paper.
Test duplicates and extreme values.
Benchmark the custom implementation against the standard library.