使用Vector时，C ++超出范围

Posted 2021-05-06

所以我通过将节点放入向量来创建二进制搜索树（BST）。这些节点存储3个值，用户输入int ID，用户输入int年龄和用户string输入名称。

将这些节点插入向量时，它们将按升序存储。

目前我正在使用两个节点。

104 10鲍勃

102史蒂夫

推回第一个节点时，没有问题;但是，当试图推回第二个节点时，我得到一个向量类抛出的out_of_bounds错误。

我相信在尝试切换这两个节点的位置时我的插入功能出了问题，但我无法准确说出问题所在。

#include "BinaryTree.h"
#include <string>
#include <iostream>
#include <vector>

using namespace std;
int index;

struct Node
{
    int ID;
    int age;
    string name;

    Node()
    {

    }

    Node(int id, int Age, string nm)
    {
        this->ID = id;
        this->age = Age;
        this->name = nm;
    }
};

vector<Node> binaryTree;


BST::BST()
{

}



void BST::start()
{
    int choice;


    cout << "What would you like to do?" << endl;
    cout << "1. Add a node to the tree" << endl;
    cout << "2. Delete a node from the tree" << endl;
    cout << "3. Find a node in the tree" << endl;
    cout << "4. Report the contents of the tree" << endl;
    cout << "5. Exit program" << endl;

    cin >> choice;

    if (choice == 1)
    {
        insert();
    }

    if (choice == 3)
    {
        find();
    }

    if (choice == 4)
    {
        report();
    }


}


void BST::insert()
{

    int ID;
    int AGE;

    string NAME;

    cout << "Please enter the ID number, age and name" << endl;
    cin >> ID >> AGE >> NAME;

    Node *tree = new Node(ID, AGE, NAME);

    if (index == 0)
    {
        binaryTree.push_back(*tree);
        index++;
    }

    if (index > 0)
    {
        if ((binaryTree.at(index - 1).ID) < ID)
        {
            binaryTree.push_back(*tree);
            index++;
        }
    }


    if (index > 0)
    {
        if ((binaryTree.at(index - 1).ID) > ID)
        {
            Node *temp = new Node();
            *temp = binaryTree.at(index - 1);
            binaryTree.at(index - 1) = *tree;

            binaryTree.at(index) = *temp;
            index++;
        }
    }

    cout << "Added! Size: " << binaryTree.size() << endl;
    cout << " " << endl;
    start();

非常感谢帮助！谢谢！

答案

执行此操作时，矢量不会调整大小：binaryTree.at(index) = *tree;

然后push_back()尝试排序

binaryTree.push_back(*tree;)
std::sort(binaryTree.begin(),binaryTree.end(),[](const Node& n1, const Node& n2){//do your comparations});

或者只是使用std::set

如果你想使用std :: vector而不崩溃，那么你的insert（）必须如下所示：

void BST::insert()
{
    int ID;
    int AGE;

    string NAME;

    cout << "Please enter the ID number, age and name" << endl;
    cin >> ID >> AGE >> NAME;

    //Node *tree = new Node(ID, AGE, NAME); // Don't use new here, there is no need in this
    Node tree(ID, AGE, NAME);

    binaryTree.push_back(tree);
    std::sort(binaryTree.begin(), binaryTree.end(), [](const Node& n1, const Node& n2)
          {
              //compare your nodes here
              return (n1.ID > n2.ID);
          });

    cout << "Added! Size: " << binaryTree.size() << endl;
    cout << " " << endl;
    start();
}

但这不是二叉树。您需要其他数据结构来创建二叉树，std::vector不能是二叉树。有一个现成的解决方案，看看std::set，它插入你需要的元素，你需要将自定义比较功能添加到std::set，一切都会好的。以下是std::set的例子：

class Node
{
public:
    Node(int id):ID(id){}
    int ID;
};

class NodeComparator
{
public:
    bool operator()(const Node& n1,const Node& n2)
    {
        return n1.ID < n2.ID;
    }
};

int main()
{
    std::set<Node, NodeComparator> set1;
    set1.insert(10);
    set1.insert(8);
    set1.insert(14);
    set1.insert(2);

    return 0;
}

这是你需要的，std::set排序提升：

另一答案

std::vector除了push_back之外还有插入元素的方法。具体来说，insert占据一个位置，在那里插入新元素。 emplace甚至更好，因为你甚至不必创建一个元素来复制到向量中，你只需传递构造函数参数。

您可以找到与std::lower_bound一起插入的适当位置。

#include <algorithm>

void BST::insert()
{
    int ID;
    int AGE;
    std::string NAME;

    std::cout << "Please enter the ID number, age and name" << std::endl;
    std::cin >> ID >> AGE >> NAME;

    auto pos = std::lower_bound(binaryTree.begin(), binaryTree.end(), 
        [](const Node& n1, const Node& n2) { return (n1.ID > n2.ID); });

    binaryTree.emplace(pos, ID, AGE, NAME);

    std::cout << "Added! Size: " << binaryTree.size() << endl;
    std::cout << " " << std::endl;
    // start(); // dubious, see below
}

顺便说一句，你的insert方法知道start正在泄露假设，你可能以后想要改变。在start中包含所有内容会好得多，例如：

void BST::start()
{
    std::cout << "What would you like to do?" << std::endl;
    std::cout << "1. Add a node to the tree" << std::endl;
    std::cout << "2. Delete a node from the tree" << std::endl;
    std::cout << "3. Find a node in the tree" << std::endl;
    std::cout << "4. Report the contents of the tree" << std::endl;
    std::cout << "5. Exit program" << std::endl;

    for(int choice; (std::cin >> choice) && (choice != 5);)
    {   
        switch (choice)
        {
        case 1: insert(); break;
        case 3: find(); break;
        case 4: report(); break;
        }
    }
}