显示倒金字塔

Question

I want to have output like this

5 4 3 2 1 2 3 4 5
  4 3 2 1 2 3 4
    3 2 1 2 3
      2 1 2
        1

How can I leave a space on left hand side ?

public class Exercise4_17 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the number of lines: ");
        int num = input.nextInt();
        Exercise4_17 exe = new Exercise4_17();
        exe.displayPyramid(num);
    }

    private void displayPyramid(int num) {

        for (int i = num; i >= 1; i--) {
            for (int space = 1; space <= num - i; ++space) {
                System.out.print("  ");
            }
            for (int k = num; k >= 1; k--) {
                System.out.print(k + " ");
            }

            for (int j = 2; j <= num; j++) {
                System.out.print(j + " ");
            }
            System.out.println();
            num--;
        }
    }
}

My output

Enter the number of lines: 5
5 4 3 2 1 2 3 4 5 
4 3 2 1 2 3 4 
3 2 1 2 3 
2 1 2 
1 

Answer 1

Your code is very close. First, as a matter of style, I would use the same variable name for the second loop ( j is jarring, just use k ). Second, and the real problem, you are modifying num in your loop. Save the initial value before you loop and use that for your space calculation. Like,

final int initial = num; // <-- add this
for (int i = num; i >= 1; i--) {
    for (int space = 1; space <= initial - i; ++space) { // <-- use initial instead of num
        System.out.print("  ");
    }
    for (int k = num; k >= 1; k--) {
        System.out.print(k + " ");
    }
    for (int k = 2; k <= num; k++) { // <-- j should still work of course...
        System.out.print(k + " ");
    }
    System.out.println();
    num--;
}

Answer 2

Hope this helps.

import java.util.Scanner;
public class MainClass {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        //Taking noOfRows value from the user
        System.out.println("How Many Rows You Want In Your Pyramid?");
        int noOfRows = sc.nextInt();
        //Initializing rowCount with noOfRows
        int rowCount = noOfRows;
        System.out.println("Here Is Your Pyramid");
        //Implementing the logic
        for (int i = 0; i < noOfRows; i++) {
            //Printing i*2 spaces at the beginning of each row
            for (int j = 1; j <= i*2; j++) {
                System.out.print(" ");
            }
            //Printing j where j value will be from 1 to rowCount
            for (int j = rowCount; j >= 1; j--) {
                 System.out.print(j+" ");
             }
             //Printing j where j value will be from rowCount-1 to 1
             for (int j = 2; j <= rowCount; j++) {
                    System.out.print(j+" ");
            }
            System.out.println();
            //Decrementing the rowCount
            rowCount--;
        }
    }
}

ref link

Output: How Many Rows You Want In Your Pyramid? 5 Here Is Your Pyramid

 5 4 3 2 1 2 3 4 5

    4 3 2 1 2 3 4 

     3 2 1 2 3 

       2 1 2 

         1