Question

#include <iostream>
#include <vector>
#include <string>

using namespace std;

#define LOWERCASE_ALPHABET_SiZE 26

typedef int (*ptr) (char );

inline int charToIndex(char a) { return a - 'a'; };

class trienode
{
    private:
        vector< trienode* > child;
        bool leaf;
    public:
        trienode(int );
        ~trienode();
        void initialiseChild(int i);
        trienode* getChild(int i);
        void setLeaf() { leaf = true; };
        bool isLeaf() { return leaf; };
};

trienode::trienode(int size)
{
    for(int i = 0; i < size; i++)
    {
        child.push_back(NULL);
    }
    leaf = false;
}

trienode::~trienode()
{
    for(int i = 0; i < child.size(); i++)
    {
        delete child.at(i);
        child.at(i) = NULL;
    }
}

void trienode::initialiseChild(int i)
{
    child.at(i) = new trienode(child.size());
}

trienode* trienode::getChild(int i)
{
    return child.at(i);
}

class trie
{
    private:
        trienode* root;
        ptr toIndex;
    public:
        trie(int , ptr );
        ~trie();
        void insert(const string& ref);
        bool search(const string& ref);
};

trie::trie(int size, ptr toIndex) : toIndex(toIndex), root(new trienode(size)) { }

trie::~trie()
{
    cout << "In destructor trie" << endl;
    delete root;
    root = NULL;
}

void trie::insert(const string& ref)
{
    int size = ref.size();
    trienode* root = root;
    for(int i = 0; i < size; i++)
    {
        int index = toIndex(ref[i]);
        if(root->getChild(index) == NULL) // crashing in getChild()
        {
            root->initialiseChild(index);
        }
        root = root->getChild(index);
    }
    root->setLeaf();
}

bool trie::search(const string& ref)
{
    trienode* root = root;
    int size = ref.size();
    for(int i = 0; i < size && root != NULL; i++)
    {
        int index = toIndex(ref[i]);
        if((root = root->getChild(index)) == NULL)
        {
            break;
        }
    }
    return (root != NULL && root->isLeaf());
}

int main(int argc,char* argv[])
{
    trie* altrie = new trie(LOWERCASE_ALPHABET_SiZE, charToIndex);
    int n;
    string temp;
    cin >> n;
    for(int i = 0; i < n; i++)
    {
        cin >> temp;
        altrie->insert(temp);
    }
    int k;
    for(int i = 0; i < k; i++)
    {
        cin >> temp;
        if(altrie->search(temp))
        {
            cout << temp << " exists in the trie" << endl;
        }
        else
        {
            cout << temp << " doesn`t exist in the trie" << endl;
        }
    }
    return 0;
}

我创建Trie是通过提供每个级别中没有的子级和函数指针来将给定的字符转换为索引。之后我创建了trie的根节点，当我插入第一个字符串时，它在getChild函数中获得了Segmentation Fault

首先要说明崩溃背后的原因。解释我如何改进trie的实现。

Answer 1

您对成员和局部变量使用相同的名称，如下所示：

trienode* root = root;

编译器无法分辨本地root和trie :: root之间的差异，因此您将其分配给自己。

使用向量c ++实现trie实现中的分段错误

1 个答案: