What is the difference between std::transform and std::for_each?

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**transform** — modifies and stores result. **for_each** — modifies in place. **std::transform:** - Applies function to each element. - Stores result in output range. - Returns output iterator. ```cpp std::vector v = {1, 2, 3}; std::vector result(v.size()); // Square each element std::transform(v.begin(), v.end(), result.begin(), [](int x) { return x * x; } ); // result: 1, 4, 9 // In-place std::transform(v.begin(), v.end(), v.begin(), [](int x) { return x * 2; } ); ``` **std::for_each:** - Applies function to each element. - Modifies in place. - No output range. ```cpp std::for_each(v.begin(), v.end(), [](int& x) { x *= 2; } ); ``` **Key difference:** - **transform** — creates new sequence. - **for_each** — modifies existing.

C++: What is the difference between std::transform and std::for_each?