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I'm not sure if the following code can cause redundant calculations, or is it compiler-specific?
for (int i = 0; i < strlen(ss); ++i) { // blabla } Will strlen() be calculated every time when i increases?
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The time complexity of standard strlen is O(n). Since all trailing characters are '\0', we can use binary search. By comparing middle two elements with '\0', we can decide whether we need to recur for left half or right half. IF one of them is \0, then we found the first occurrence.
Ok, I need to add some explanation. My application is getting a string from a shared memory (which is of some length), therefore it could be represented as an array of characters. If there is a bug in the library writing this string, then the string would not be zero terminated, and the strlen could fail.
If you're using a char[] , then you can use sizeof(str) - 1 instead.
For C++ strings, there's no reason to use strlen . Just use string::length : Clarity: The length() (or size() ) member functions unambiguously give back the length of the string.
Yes, strlen() will be evaluated on each iteration. It's possible that, under ideal circumstances, the optimiser might be able to deduce that the value won't change, but I personally wouldn't rely on that.
I'd do something like
for (int i = 0, n = strlen(ss); i < n; ++i) or possibly
for (int i = 0; ss[i]; ++i) as long as the string isn't going to change length during the iteration. If it might, then you'll need to either call strlen() each time, or handle it through more complicated logic.
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