在c ++

Question

我试图通过在线查看一些示例来使用c ++实现后缀树。我遇到指针问题，我无法解决它。非常感谢任何帮助。

/*
* Implement suffix array to print the maximum suffix substring in a string
* Algorithm:
* Build a suffix tree and find the lowest node with multiple children
*
*/
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <ctype.h>

using namespace std;

struct node{
    char ch;
    node* next[26];
    int treeHeight;
    int childCount;
    int end = 0;
};

void insertSuffixIntoTree(node*& root, string suffix){
   if (suffix.size() == 0){
      return;
   }
   char c = suffix[0];
   int index = tolower(c) - 'a';
   if (root->next[index] == NULL){
     root->next[index] = new node();
     for (int k = 0; k < 26; k++){
        root->next[index]->next[k] = NULL;
     }
     root->next[index]->ch = tolower(c);
     if (suffix.size() == 1){
        root->next[index]->end = 1;
     }
   }
   suffix.erase(suffix.begin());
   insertSuffixIntoTree(root->next[index], suffix);
}

void buildSuffixTree(node* root, string str){
    if (root == NULL) cout << "CRAP" << endl;
    for (int i = str.size() - 1; i >= 0; i--){
        string suffix = str.substr(i);
        cout << "suffix is " << suffix << endl;
        insertSuffixIntoTree(root, suffix);
    }
}


void printSuffixTree(node* root, string str){
    if (root->end){
        cout << str << endl;
        return;
    }
    for (int i = 0; i<26; i++){
        while (root->next[i]){
            str += root->ch;
            return printSuffixTree(root->next[i],str);
        }
    }
}

int main() {
    string str;
    node* suffixRoot = new node();
    suffixRoot->ch = ' ';
    for (int i = 0; i < 26; i++){
        suffixRoot->next[i] = NULL;
    }
    cout << "enter the string" << endl;
    cin >> str;
    buildSuffixTree(suffixRoot, str);
    //string result = findMaxSuffix(suffixRoot,str);
    //cout<<"result is "<<result<<endl;
    string result = "";
    printSuffixTree(suffixRoot,result);
    getchar();
    return 0;
}

错误发生在buildSuffixTree方法内的insertIntoSuffixTree方法中。我的理解是我失去了我开始时的指针地址。有关如何解决这个问题的任何想法？

Answer 1

很抱歉给您带来不便。我修改了代码，如下所示：

/*
* Implement suffix array to print the maximum suffix substring in a string
* Algorithm:
* Build a suffix tree and find the lowest node with multiple children
*
*/
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <ctype.h>

using namespace std;

struct node{
    char ch;
    node* next[26];
    int treeHeight;
    int childCount;
    int end = 0;
};

void insertSuffixIntoTree(node* root, string suffix){
   if (suffix.size() == 0){
      return;
   }
   char c = suffix[0];
   int index = tolower(c) - 'a';
   if (root->next[index] == NULL){
     root->next[index] = new node();
     for (int k = 0; k < 26; k++){
        root->next[index]->next[k] = NULL;
     }
     root->next[index]->ch = tolower(c);
     if (suffix.size() == 1){
        root->next[index]->end = 1;
     }
   }
   suffix.erase(suffix.begin());
   insertSuffixIntoTree(root->next[index], suffix);
}

void buildSuffixTree(node* root, string str){
    if (root == NULL) cout << "CRAP" << endl;
    for (int i = str.size() - 1; i >= 0; i--){
        string suffix = str.substr(i);
        cout << "suffix is " << suffix << endl;
        insertSuffixIntoTree(root, suffix);
    }
}

bool checkEmptyVector(node * leaf){
    for (int i = 0; i < 26; i++){
        if (leaf->next[i] != NULL){
            return false;
        }
    }
    return true;
}

void printSuffixTree(node* root, string str){
    if (root->end){
        cout << str << endl;
    }
    if (checkEmptyVector(root)){
        return;
    }
    for (int i = 0; i<26; i++){
        //cout << "inside for loop, i is " << i << endl;
        while (root->next[i]){

            str += root->next[i]->ch;
            printSuffixTree(root->next[i],str);
            break;
        }
    }
}

int main() {
    string str;
    node* suffixRoot = new node();
    suffixRoot->ch = ' ';
    for (int i = 0; i < 26; i++){
        suffixRoot->next[i] = NULL;
    }
    cout << "enter the string" << endl;
    cin >> str;
    buildSuffixTree(suffixRoot, str);
    //string result = findMaxSuffix(suffixRoot,str);
    //cout<<"result is "<<result<<endl;
    string result = "";
    printSuffixTree(suffixRoot,result);
    getchar();
    return 0;
}