#include <iostream>
using namespace std;
   int main()
{
    int j, rows;
       cout <<"Enter number of rows: ";
    cin >> rows;
       for(int i = 1, k = 0; i <= rows; ++i, k = 0)
    {
        for(j = 1; j <= rows-i; ++j)
        {
            cout <<"  ";
        }
        while(k != 2*i-1)
        {
            cout << "* ";
            ++k;
        }
        cout << endl;
    }    
    return 0;
}

Enter number of rows : 7   
            * 
          * * * 
        * * * * * 
      * * * * * * * 
    * * * * * * * * * 
  * * * * * * * * * * * 
* * * * * * * * * * * * *