find all the palindrome substring in a given string

1#include <iostream>
2#include <string>
3#include <unordered_set>
4using namespace std;
5
6// expand in both directions of low and high to find all palindromes
7void expand(string str, int low, int high, auto &set)
8{
9	// run till str[low.high] is a palindrome
10	while (low >= 0 && high < str.length()
11			&& str[low] == str[high])
12	{
13		// push all palindromes into the set
14		set.insert(str.substr(low, high - low + 1));
15
16		// expand in both directions
17		low--, high++;
18	}
19}
20
21// Function to find all unique palindromic substrings of given string
22void allPalindromicSubstrings(string str)
23{
24	// create an empty set to store all unique palindromic substrings
25	unordered_set<string> set;
26
27	for (int i = 0; i < str.length(); i++)
28	{
29		// find all odd length palindrome with str[i] as mid point
30		expand(str, i, i, set);
31
32		// find all even length palindrome with str[i] and str[i+1] as
33		// its mid points
34		expand(str, i, i + 1, set);
35	}
36
37	// print all unique palindromic substrings
38	for (auto i : set)
39		cout << i << " ";
40}
41
42int main()
43{
44	string str = "google";
45
46	allPalindromicSubstrings(str);
47
48	return 0;
49}