std :: vector：需要保留？

for（int jj = 0; jj< en; ++ jj） vec.push_back（jj）; for（int jj = 0 ; jj< en; ++ jj） cout<< vec [jj]<< endl; 返回0; } No, you could do that (use reserve), or, use push_back() int main(int argc, const char* argv[]){int en = 10;vector<int vec; for (int jj = 0; jj < en; ++jj)vec.push_back(jj);for (int jj = 0; jj < en; ++jj)cout << vec[jj] << endl; return 0;} 不，但你需要以某种方式填充向量。你可以在 构建时，或者使用push_back，insert或resize来实现。 另一方面，reserve（）方法没有增长向量。 No, but you need to fill the vector somehow. You can do that either uponconstruction, or by using push_back, insert, or resize. The reserve() method, on the other hand does not grow the vector. 它没有。您正在观察未定义行为的表现。 It does not. You are observing a manifestation of undefined behavior. 对于未定义的行为将如何表现，没有任何期望。 从实施的质量来看，如果你在打开断言的情况下编译程序，我会希望看到一个中止 。 There are no expectations as to how undefined behavior will show itself. From a quality of implementation point of view, would want to see an abortif you compile the program with assertions turned on. 尝试类似 cout<< vec.size（）<<结束; 并思考你得到的含义。 Try something like cout << vec.size() << endl; and ponder the meaning of what you get. Best Kai-Uwe Bux Best Kai-Uwe Bux 这篇关于std :: vector：需要保留？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！