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C/C++ Algorithms

Linear Search

Find a target in unsorted data.

What is Linear Search?

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

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

C
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));
}
Result of running the code
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';
}
Result of running the code
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.

C

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.

Practice with a challenge

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