all permutations of a string c++ code example

Example 1: find all occurrences of a substring in a string c++

#include <string>
#include <iostream>

using namespace std;

int main()
{
    string s("hello hello");
    int count = 0;
    size_t nPos = s.find("hello", 0); // first occurrence
    while(nPos != string::npos)
    {
        count++;
        nPos = s.find("hello", nPos + 1);
    }

    cout << count;
};

Example 2: find all permutations of a string

void permute(string a, int l, int r)  
{  
    // Base case  
    if (l == r)  
        cout<<a<<endl;  
    else
    {  
        // Permutations made  
        for (int i = l; i <= r; i++)  
        {  
  
            // Swapping done  
            swap(a[l], a[i]);  
  
            // Recursion called  
            permute(a, l+1, r);  
  
            //backtrack  
            swap(a[l], a[i]);  
        }  
    }  
}

Example 3: how to print all permutations of a string

void permutation(string s)
{
    sort(s.begin(),s.end());
	do{
		cout << s << " ";
	}
    while(next_permutation(s.begin(),s.end()); // std::next_permutation
    
    cout << endl;
}