打印菱形图形

编程打印下列图形：

                                   A

                                 ABC

                               ABCDE

                             ABCDEFG

                           ABCDEFGHI

                         ABCDEFGHIJK

                       ABCDEFGHIJKLM

                     ABCDEFGHIJKLMNO

                   ABCDEFGHIJKLMNOPQ

                 ABCDEFGHIJKLMNOPQRS

                   ABCDEFGHIJKLMNOPQ

                     ABCDEFGHIJKLMNO

                       ABCDEFGHIJKLM

                         ABCDEFGHIJK

                           ABCDEFGHI

                            ABCDEFG

                              ABCDE

                                ABC

                                  A

#include <tchar.h>
#include <string>
#include <iostream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    string strFull = "ABCDEFGHIJKLMNOPQRS";
    size_t charNum = strFull.length();
    int i = 1; // how many chars on a row.
    int cnt = 0; // how many rows we have printed.
    bool bGrow = true; // string increase or decrease direction flag.
    while (cnt < charNum)
    {
        int spaceNum = (int)(charNum - i) / 2; // how many spaces we need to print.        
        string strSpace(spaceNum, ' ');
        string realStr = strFull.substr(0, i);
        cout << strSpace << realStr << strSpace << endl;

        if(i == charNum) // after printing the whole string, reverse the print rule.
        {
            bGrow = false;
        }

        if(bGrow)
            i += 2;
        else
            i -= 2;

        cnt++;
    }
    
    return 0;
}