clear和delete的区别

在C++中，`clear()`和`delete`是两个不同的操作，分别应用于容器（如vector、list等）和动态分配的对象（如new出来的内存块）。

1. `clear()`：
- 对于容器（如`std::vector`），`clear()`方法用于清空容器的内容，即删除其中的所有元素，但并不释放内存。容器本身的大小不会改变，只是内部的元素引用无效了。

   std::vector<int> v;
   v.push_back(1);
   v.push_back(2);
   v.clear();  // 现在v为空，但长度仍然是2

2. `delete`：
- 对于动态分配的内存（通常用`new`关键字创建），`delete`操作用于释放之前用`new`申请的空间，防止内存泄漏。如果是一个指针指向的对象，需要先`delete`指针本身，然后才能对指针进行赋值为NULL或者其他操作。

   int* p = new int;  // 动态分配内存
   *p = 42;
   delete p;         // 释放内存
   p = nullptr;       // 或者置空

总结来说，`clear()`主要用于处理数据结构中的状态，保持容器本身的存在；而`delete`则用于管理内存，确保不再有对该内存的引用，以便垃圾回收机制工作。

相关问题

给下列程序添加英文注释： MoveBase::~MoveBase(){ recovery_behaviors_.clear(); delete dsrv_; if(as_ != NULL) delete as_; if(planner_costmap_ros_ != NULL) delete planner_costmap_ros_; if(controller_costmap_ros_ != NULL) delete controller_costmap_ros_; planner_thread_->interrupt(); planner_thread_->join(); delete planner_thread_; delete planner_plan_; delete latest_plan_; delete controller_plan_; planner_.reset(); tc_.reset(); }

// Destructor for the MoveBase class
MoveBase::~MoveBase(){
// Clear the vector of recovery behaviors
recovery_behaviors_.clear();
// Delete the dynamic reconfigure server
delete dsrv_;
// Delete the action server
if(as_ != NULL)
delete as_;
// Delete the costmap for the planner
if(planner_costmap_ros_ != NULL)
delete planner_costmap_ros_;
// Delete the costmap for the controller
if(controller_costmap_ros_ != NULL)
delete controller_costmap_ros_;
// Interrupt the planner thread and wait for it to finish
planner_thread_->interrupt();
planner_thread_->join();
// Delete the planner thread
delete planner_thread_;
// Delete the planner plan
delete planner_plan_;
// Delete the latest plan
delete latest_plan_;
// Delete the controller plan
delete controller_plan_;
// Reset the planner and the trajectory controller
planner_.reset();
tc_.reset();
}

for i in range(len(data)): if data[i,-1] == 2: clear_arr = np.delete(data,i,axis=0) print(clear_arr)

This code iterates through each row in the "data" array using a for loop with the range function.

For each row, it checks if the last element (indicated by "-1") is equal to 2.

If the last element is 2, it uses the numpy "delete" function to remove that entire row from the "data" array, creating a new array called "clear_arr".

Finally, it prints the "clear_arr" array.

Overall, this code appears to be removing any rows from the "data" array where the last element is equal to 2.