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String complexity
Автор rookiegang, история, 7 лет назад, По-английски

What is complexity of adding char in front of the string like s = c + s?

Because when I tested on c++ with code, its like O(1), but i think (but not sure then i ask here) i ever submitted at codeforces with this method, in O(n) loop then its get TLE (so the complexity O(n^2)), then i changed that part with other O(1) part then got AC.

What is complexity of adding on string like s = s2 + s1 with s1 is small string with length < 10 and s2 is n-long string?
What is complexity of adding on string like s = s1 + s2 with s1 is small string with length < 10 and s2 is n-long string?

Thank you codeforces community

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Adding a char in front of a string is always linear in length of the string.

In general, concatenating two strings will be linear in lengths of both strings.

However, if the first string is an rvalue, then the second one will be just appended to it. If appending doesn't cause the first string to reach its capacity, you can expect it to take time proportional to the length of the second string.

For example, the following code will take O(N^2) time:

    std::string a;
    for (int i = 0; i < N; ++i) {
      a = a + "xy";
    }

And the following code will take O(N) time:

    std::string a;
    for (int i = 0; i < N; ++i) {
      a = std::move(a) + "xy";
    }
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