Printing Pascal Triangle seems like an easy problem, however, it is not that easy to print a good-looking Pascal Triangle.

To print the Pascal Triangle, for each line, first print spaces to the left of numbers, and then print digit numbers.

To calculate Pascal numbers, two assays can be used: one array to store numbers of above line, the other array to store numbers of this line. The first line has 1 number(1), the second lien has 2 numbers(1 1), the third line has three numbers(1 2 1) and so on.

To make the Pascal Triangle more readable, print spaces between two neighbor  numbers in the same line.


// Pascal triangle
#include <iostream>
#include <iomanip>
#include <cstring>
using namespace std;

const int WIDTH=7;
int main()
{
int* oldarr=new int[WIDTH]; // store numbers of above row
int* newarr=new int[WIDTH]; // store numbers of current row

for(int i=0;i<WIDTH;++i) // cntrol row counting
{
for(int j=0;j<WIDTH-i-1;++j) // left space
cout << setw(2) << " ";

// set default boundary numbers
newarr[0]=1;
if(i<=1)
newarr[i]=1;

if(i<=2)
{
for(int k=1;k<i;++k)
newarr[k]=oldarr[k-1]+oldarr[k];
}
memcpy(oldarr,newarr,sizeof(int)*WIDTH);

// Print the middle part
int idx=0;
int flag=(WIDTH-i-1)%2;
for(int j=WIDTH-i-1;j<WIDTH+i;++j)
{
if(j%2==flag)
{
cout << setw(2) << newarr[idx++];
} else {
cout << setw(2) << " ";
}
}

//for(int j=WIDTH+i;j&lt;WIDTH;++j) // Print right space, if you like
//	cout&lt;&lt;setw(4)&lt;&lt;&quot; &quot;;

cout << endl;
}

delete [] oldarr;
delete [] newarr;

return 0;
}


The output looks like:

             1
1   1
1   2   1
1   3   3   1
1   4   6   4   1
1   5  10  10   5   1
1   6  15  20  15   6   1