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20. Hollow Diamond Star Pattern

Example

Pattern 20

\(N = 5\)

\[\Large
\begin{align}
    &\ast\ \ \ \ \ \ \ \  \ \ \ \ \ \ \  \ \ \ \ \ \ \ \ \ \ast \\
    &\ast\ast\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ast\ast \\
    &\ast\ast\ast\ \ \ \ \ \ \ \ \ \ \ \ \ast\ast\ast \\
    &\ast\ast\ast\ast\ \ \ \ \ \ \ast\ast\ast\ast \\
    &\ast\ast\ast\ast\ast\ast\ast\ast\ast\ast \\
    &\ast\ast\ast\ast\ \ \ \ \ \ \ast\ast\ast\ast \\
    &\ast\ast\ast\ \ \ \ \ \ \ \ \ \ \ \ \ast\ast\ast \\
    &\ast\ast\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ast\ast \\
    &\ast\ \ \ \ \ \ \ \  \ \ \ \ \ \ \  \ \ \ \ \ \ \ \ \ \ast \\
\end{align}
\]
printTriangle.cpp 
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#include <bits/stdc++.h>
using namespace std;

void printTriangle(int n) {
    for(int i=1; i<=n; i++) {
        for(int j=0; j<i; j++) {
            cout << "*";
        }
        for(int j=0; j<2*(n-i); j++) {
            cout << " ";
        }
        for(int j=0; j<i; j++) {
            cout << "*";
        }
        cout << endl;
    }
    for(int i=n-1; i>0; i--) {
        for(int j=0; j<i; j++) {
            cout << "*";
        }
        for(int j=0; j<2*(n-i); j++) {
            cout << " ";
        }
        for(int j=0; j<i; j++) {
            cout << "*";
        }
        cout << endl;
    }
}

int main(void) {
    int n;
    cin >> n;
    printTriangle(n);
    return 0;
}

Input: 5
Output: 

*        *
**      **
***    ***
****  ****
**********
****  ****
***    ***
**      **
*        *