I have a small assignment where I have to use a 2d array to produce Pascal's triangle. Here is my code, and it works. There is an extra credit opportunity if I display the triangle like so:
However, my spacing is not formatted like that. it simply displays the numbers all lined up on the left. its hard to describe but if you run it you will see what I mean.
Here is my code:
public class Pascal {
public static final int ROW = 16;
public static void main(String[] args) {
int[][] pascal = new int[ROW + 1][];
pascal[1] = new int[1 + 2];
pascal[1][1] = 1;
for (int i = 2; i <= ROW; i++) {
pascal[i] = new int[i + 2];
for (int j = 1; j < pascal[i].length - 1; j++) {
pascal[i][j] = pascal[i - 1][j - 1] + pascal[i - 1][j];
}
}
for (int i = 1; i <= ROW; i++) {
for (int j = 1; j < pascal[i].length - 1; j++) {
System.out.print(pascal[i][j] + " ");
}
System.out.println();
}
}
}
If someone could help me figure out how to add the correct spacing to my program to produce the output desired in the picture, that would be great. I know I need to put a System.out.print(" ")
somewhere. I just dont know where.
Pascal's Triangle in C++ The top row is numbered as n=0, and in each row are numbered from the left beginning with k = 0. Each number is found by adding two numbers which are residing in the previous row and exactly top of the current cell. It is also being formed by finding (𝑛𝑘) for row number n and column number k.
What is Pascal's Triangle? Pascal's triangle is the triangular array of numbers that begins with 1 on the top and with 1's running down the two sides of a triangle. Each new number lies between two numbers and below them, and its value is the sum of the two numbers above it.
Here I had modified your code, it prints wonderfully for ROW size till 13, because of the limitation of my console window:
import java.util.*;
public class Pascal {
public static final int ROW = 12;
private static int max = 0;
public static void main(String[] args) {
int[][] pascal = new int[ROW + 1][];
pascal[1] = new int[1 + 2];
pascal[1][1] = 1;
for (int i = 2; i <= ROW; i++) {
pascal[i] = new int[i + 2];
for (int j = 1; j < pascal[i].length - 1; j++) {
pascal[i][j] = pascal[i - 1][j - 1] + pascal[i - 1][j];
String str = Integer.toString(pascal[i][j]);
int len = str.length();
if (len > max)
max = len;
}
}
for (int i = 1; i <= ROW; i++) {
for (int k = ROW; k > i; k--)
System.out.format("%-" + max + "s", " ");
for (int j = 1; j < pascal[i].length - 1; j++)
System.out.format("%-" + (max + max) + "s", pascal[i][j]);
System.out.println();
}
}
}
Output:
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
1 7 21 35 35 21 7 1
1 8 28 56 70 56 28 8 1
1 9 36 84 126 126 84 36 9 1
1 10 45 120 210 252 210 120 45 10 1
1 11 55 165 330 462 462 330 165 55 11 1
You're encountering spacing issues because you need to add whitespace to certain numbers to accommodate space that larger numbers occupy. First determine what the largest number you plan to print is (programmatically). Then determine the number of digits in that number log(n). You can then use this number to print whitespace for numbers that have less digits than your largest number to make your printing look nicer.
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