如何找到最长子串的长度，使其连续重复

Question

假设我有一个类似的字符串-

str = "cadaabaabbc";

所需的输出是 6，它占索引 3 到 8 的 "aabaab"。 有人可以从初学者的角度建议我一个有效的算法吗？

谢谢。

Answer 1

https://en.wikipedia.org/wiki/Suffix_array

#include <iostream>
#include <vector>
#include <unordered_map>
#include <string>
using namespace std;

class Node
{
public:
    char ch;
    unordered_map<char, Node *> children;
    vector<int> indexes; //store the indexes of the substring from where it starts
    Node(char c) : ch(c) {}
};

int maxLen = 0;
string maxStr = "";

void insertInSuffixTree(Node *root, string str, int index, string originalSuffix, int level = 0)
{
    root->indexes.push_back(index);

    // it is repeated and length is greater than maxLen
    // then store the substring
    if (root->indexes.size() > 1 && maxLen < level)
    {
        maxLen = level;
        maxStr = originalSuffix.substr(0, level);
    }

    if (str.empty())
        return;

    Node *child;
    if (root->children.count(str[0]) == 0)
    {
        child = new Node(str[0]);
        root->children[str[0]] = child;
    }
    else
    {
        child = root->children[str[0]];
    }

    insertInSuffixTree(child, str.substr(1), index, originalSuffix, level + 1);
}

int main()
{
    string str = "cadaabaabbc";//"missiissippi";
    Node *root = new Node('@');

    //insert all substring in suffix tree
    for (int i = 0; i < str.size(); i++)
    {
        string s = str.substr(i);
        insertInSuffixTree(root, s, i, s);
    }

    int startIndex = str.find(maxStr);
    cout << startIndex << " to " << startIndex + (2 * maxLen) - 1;

    return 1;
}