C++利用循环打印菱形星号，字母，空心

外层循环控制行，内层循环控制列

#include <iostream>
using namespace std;
int main()
{
 for (int i = 0; i < 4; i++) {
  for (int j = 0; j <= 2 - i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 2 * i; j++) {
   cout << "*";
  }
  cout << endl;
 }
 for (int i = 0; i < 3; i++) {
  for (int j = 0; j <=  i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 4 - 2 * i; j++) {
   cout << "*";
  }
  cout << endl;
 }
 system("pause");
}

#include <iostream>
using namespace std;
int main()
{
 for (int i = 0; i < 4; i++) {
  for (int j = 0; j <= 2 - i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 2 * i; j++) {
   cout << char('A' + i);
  }
  cout << endl;
 }
 for (int i = 0; i < 3; i++) {
  for (int j = 0; j <=  i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 4 - 2 * i; j++) {
   cout << char('C' - i);
  }
  cout << endl;
 }
 system("pause");
}

#include <iostream>
using namespace std;
int main()
{
 for (int i = 0; i < 4; i++) {
  for (int j = 0; j <= 2 - i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 2 * i; j++) {
   if (j == 0 || j == 2 * i) {
    cout << "*";
   }
   else {
    cout << " ";
   }
  }
  cout << endl;
 }
 for (int i = 0; i < 3; i++) {
  for (int j = 0; j <=  i; j++) {
   cout << " ";
  }
  for (int j = 0; j <= 4 - 2 * i; j++) {
   if (j == 0 || j == 4 - 2 * i) {
    cout << "*";
   }
   else {
    cout << " ";
   }
  }
  cout << endl;
 }
 system("pause");
}