c++ detailed note

本文详细解析了C++中vector容器的两种添加元素方式:emplace_back与push_back的区别。前者直接在vector内存中创建对象,后者则复制后再拷贝。探讨了vector在超过容量时的内存扩展策略及拷贝细节。

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vector::emplace_back:在vector内存中直接创建对象
vector::push_back:将对象复制后拷贝到vector内存中
vector添加元素超过capacity时候,vector扩展2倍内存,把运来的数据拷贝到新的内存中,并free掉原来的内存空间,包括其中的对象。注意浅拷贝和深拷贝问题。

### C++ P1088 Problem Solution and Information The provided references include a code snippet related to Binary Indexed Trees (Fenwick Tree)[^1], as well as an unrelated reference concerning issues with garbage collectors[^2]. However, no specific details about the **C++ P1088 problem** were found within these sources. To address this query comprehensively: #### Understanding Fenwick Trees A Fenwick tree is used for efficient range queries and updates on arrays. The `sum` function calculates the prefix sum up to index \(i\), while the `add` function modifies values at specified indices by adding \(x\) to them. This structure supports operations such as calculating cumulative sums efficiently in logarithmic time complexity \(\mathcal{O}(\log n)\). Here’s how it works based on the given implementation: ```cpp int bit[MAX_N + 1]; int n; // Function to calculate prefix sum from start till 'i' int sum(int i) { int gg = 0; while (i > 0) { gg += bit[i]; i -= i & (-i); } return gg; } // Function to update value at position 'i' by adding 'x' void add(int i, int x) { while (i <= n) { bit[i] += x; i += i & (-i); } } ``` This algorithm can be applied when solving dynamic array-based problems requiring frequent modifications alongside querying ranges. #### Addressing Garbage Collector Issues Although not directly relevant here, one should note potential pitfalls involving memory management systems like garbage collection mentioned earlier. These challenges typically arise due to performance overheads introduced during runtime cleanup processes but aren't pertinent unless working under certain constraints where manual control over resources becomes necessary. For locating precise solutions regarding **Problem P1088**, consider exploring online competitive programming platforms hosting similar questions categorized appropriately according to difficulty levels or topics covered therein—such sites often provide sample test cases along detailed explanations after submission attempts conclude successfully too!
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