Develop Reference

Using nested For Loops to create a table of numbers and stars

I need to print a table that looks like this if the user entered a 5 using nested for loops:
****5
***45
**345
*2345
12345
I've been working on this for hours and the closest I got was:
int size = scan.nextInt();
for (int i = 1; i <= size; i++)
{
for (int star = size-1; star >= i; star--)
System.out.print("*");
for (int k = 1; k <= i; k++)
System.out.print(i);
System.out.println();
}
Which outputs this:
****1
***12
**123
*1234
12345

You have too many loops; I find it easier to reason about zero based looping so I'm going to use that. Iterate i and j from 0 to size. If j + 1 is greater than size - i - 1 then we want to print j + 1. Otherwise, we want a star. Like,
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++) {
if (j + 1 > size - i - 1) {
System.out.print(j + 1);
} else {
System.out.print('*');
}
}
System.out.println();
}
For size = 5 that outputs (as requested)
****5
***45
**345
*2345
12345
If you simply must have one based indices, that would be
for (int i = 1; i <= size; i++) {
for (int j = 1; j <= size; j++) {
if (j > size - i) {
System.out.print(j);
} else {
System.out.print('*');
}
}
System.out.println();
}

If you want to keep your loops and avoid if statements, you can tweak last loop by changing
for (int k = 1; k <= i; k++)
into
for (int k = 1+size-i; k <= size; k++)
Btw I also find it way easier to start loops from 0, so updated code would look like this:
int size = scan.nextInt();
for (int i = 0; i < size; i++)
{
for (int star = size-1; star > i; star--)
System.out.print("*");
for (int k = size-i; k <= size; k++)
System.out.print(k);
System.out.println();
}
I hope it helps

My X's are being placed 1 space off in my histogram

import java.util.*;
public class HistogramGenerator {
public int getHeightOfHistogram(int[] occurences) {
// occurences = {1,0,0,0,1,0,0,0,0,1,0,0,0,2,0,0,0,0,0,0,0,0,0,0]
int max = occurences[0];
for (int i = 1; i < occurences.length; i++) {
if (occurences[i] > max) {
max = occurences[i];
}
}
return max;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter a line: ");
String sentenceEntered = sc.nextLine();
System.out.println("Letter Histogram");
HistogramGenerator histogram = new HistogramGenerator();
String letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //Map of all the characters
int[] occurences = new int[letters.length()]; //max size of all possible matches
// loop through sentenceEntered to find occurences of each character
for (int i = 0; i < sentenceEntered.length(); i++) {
int charValue = sentenceEntered.charAt(i);
int index = letters.indexOf(charValue); // index of the character we are searching for
if (index < 0)
continue;
occurences[index]++;
}
int heightOfHistogram = histogram.getHeightOfHistogram(occurences);
String[][] histogramArray = new String[heightOfHistogram][letters.length()]; //[2][26]
for (int j =0; j < occurences.length; j++) {
int numXtoInsert = occurences[j];
while(numXtoInsert > 0){
histogramArray[heightOfHistogram - numXtoInsert][j] = "X";
numXtoInsert--;
}
}
// print 26 dashes (length of letters)
for(int k=0; k < letters.length(); k++){
System.out.print("-");
}
System.out.println();
// print histogram
for(int row =0; row < histogramArray.length; row++){
for(int col=0; col < histogramArray[row].length; col++){
if (histogramArray[row][col] == null) {
System.out.print("");
continue;
}
System.out.print(histogramArray[row][col] + " ");
}
System.out.println();
}
System.out.println();
// print 26 dashes ( length of letters)
for(int u=0; u < letters.length(); u++){
System.out.print("-");
}
System.out.println();
// print all characters in letters
System.out.print(letters);
}
}
basically whatever word i put in it prints out something close to it, but not really correctly, if i type in apple for example it'll print out an X close to A, and X on P and an X close to P, and and X close to l and E.
maybe there's something wrong with the logic? I don't know, need some quick help!

The issue is with the printing logic. When you find a null value, you need to print a space. When you don't find a null value, you should not add an extra space. See below for the updated working logic:
// print histogram
for(int row =0; row < histogramArray.length; row++){
for(int col=0; col < histogramArray[row].length; col++){
if (histogramArray[row][col] == null) {
System.out.print(" ");
continue;
}
System.out.print(histogramArray[row][col]);
}
System.out.println();
}
System.out.println();

replace every second line of my triangle with a blank line for loops

instead of getting a full triangle with 5 lines of "*" how do I replace every second line with a blank line, e.g. to look like this
5
555
55555
This is my code:
for(int i = 0; i < 5; i++) {
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
for(int k = 0; k <= (i*2); k++) {
System.out.print("5");
}
System.out.println();
}

you need small modification in your code and you can get what you want.
for(int i = 0; i < 5; i++) {
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
for(int k = 0; k <= (i*2); k++) {
if(i%2==0)
System.out.print("*");
}
System.out.println();
}
check it out.

Just test for i % 2
for(int i = 0; i < 5; i++) {
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
for(int k = 0; k <= (i*2); k++) {
System.out.print(i % 2 == 0 ? "*" : " ");
}
System.out.println();
}
edit
If you want to print 5 instead or * then modify the code to use 5

Check this:
int num= 5; // 'num' denotes the number of lines
int numOfSpaces;
for(int i = 1; i <= num; i++) {
if( i%2 != 0) // checks whether the line number is odd. If odd, prints '*'
{
numOfSpaces = (num-i) / 2; // find the number of blank spaces
for(int j = 1; j <= numOfSpaces; j++) {
System.out.print(" ");
}
for(int k = 1; k <= i; k++) { // number of '*'s to be printed = current line number = i
System.out.print("*");
}
System.out.println();
}
else{
System.out.println(); // leaves every second line blank (ie.,if line number is even.)
}
}

//try this code. It may help you to achieve your output
[Check screen shot for the output of the below code][1]
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5 - i; j++)
{
System.out.print(" ");
}
for (int k = 0; k <= i; k++)
{
if(i%2!=0)
{
System.out.print(" ");
}
else{
System.out.print("* ");
}
}
System.out.println();
}

The Code below is Working now.
A simple if condition will solve your problem. Just check if the
value of i is divisible by 2. If it is true then print a
blank line. Else Print * and you are done!
* will be printed on 1st, 3rd and 5th lines.
Blank Space will be printed on 2nd and 4th lines.
public class PrintPattern{
public static void main(String []args){
int lineNo=0; // New Variable for Line Number (Can Use variable 'i' also)
for(int i = 0; i < 5; i++) {
lineNo++;
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
if(lineNo%2!=0){
for(int k = 0; k <= (i*2); k++)
System.out.print('*'); // Will print '*' (or '5') Sequence for Odd Lines - 1st, 3rd, 5th Lines
System.out.println();
}
else
System.out.println();// Will print Blank Line for Even Lines - 2nd and 4th Lines
}
}
}

Try this
for(int i = 0; i < 5; i++) {
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
for(int k = 0; k <= (i*2); k++) {
System.out.print("5"); //Use 5 instaed of * to draw
}
System.out.println();
System.out.println(); //This one will solve your problem
}
Output will be:
5
555
55555
5555555
555555555

I think that you can just enter one more print statement inside the loop:
for(int i = 0; i < 5; i++) {
System.out.println();
for(int j = i; j < 5; j++) {
System.out.print(" ");
}
for(int k = 0; k <= (i*2); k++) {
System.out.print("*");
}
System.out.println();
}
Output
*
***
*****
*******
*********

Printing diamonds from *'s

I am trying to System.out.print() a diamond out of *'s. So far I have spent a good 5 hours on trying to figure out how to reverse print the bottom triangle of the diamond.
I can worry about the spacing to complete the diamond later. (I have it worked for the most part).
If someone could explain to me what I am doing wrong and how the right way works I would greatly appreciate it.
private static void diamond()
{
int numLines = 0;
System.out.println("How many lines would you like in the Diamond?");
numLines = scan.nextInt();
if (numLines / 2 == 0) //if number is even, make odd.
{
numLines++;
}
for(int i = 0; i <= numLines ; i++) // Controls #Lines
{
if(i <= numLines / 2)
{
for(int j = 0; j < i * 2 - 1; j++) // Controls #Stars small upright triangle
{
System.out.print("*");
}
}
else
{
for(int k = numLines; k > i / 2; k--) // Controls # of spaces
{
System.out.print("*");
}
/*for(int j = numLines/2 - i, l = i; l > j; j++) // Controls #Stars small upright triangle
{
String stars = "*";
System.out.print(stars);
}*/
}
System.out.println("");
}
}
`

What happens to your attempt is that you loop through the half (of the lines) of your diamond [the number of lines in second/first half] times.
You'd want to do a if-statement each loop, not an if and a for in each loop

Probably you want this
Just adjust it for user input values
public static void main(String[] args) {
System.out.print("Reverse diamond: \n");
for (int i = 1; i < 10; i += 2) {
for (int j = 0; j < 9 - i / 2; j++)
System.out.print(" ");
for (int j = 0; j < i; j++)
System.out.print("*");
System.out.print("\n");
}
System.out.print("\n\nDiamond from starts: \n");
for (int i = 7; i > 0; i -= 2) {
for (int j = 0; j < 9 - i / 2; j++)
System.out.print(" ");
for (int j = 0; j < i; j++)
System.out.print("*");
System.out.print("\n");
}
}
output:

Asterisk in Nested loops, Java

I am trying to make my code print out the Asterisk in the image, you see below. The Asterisk are align to the right and they have blank spaces under them. I can't figure out, how to make it go to the right. Here is my code:
public class Assn4 {
public static void main(String[] args) {
for (int i = 0; i <= 3; i++) {
for (int j = 0; j <= i; j++) {
System.out.print("*");
}
for (int x = 0; x <= 1; x++) {
System.out.println(" ");
}
for (int j = 0; j <= i; j++) {
System.out.print("*");
}
}
System.out.println();
}
}

Matrix problems are really helpful to understand loops..
Understanding of your problem:
1) First, printing star at the end- That means your first loop should be in decreasing order
for(int i =7;i>=0; i+=i-2)
2) Printing star in increasing order- That means your second loop should be in increasing order
for(int j =0;j<=7; j++)
Complete code:
for(int i =7;i>=0; i=i-2){ // i=i-2 because *s are getting incremented by 2
for(int j =0;j<=7; j++){
if(j>=i){ // if j >= i then print * else space(" ")
System.out.print("*");
}
else{
System.out.print(" ");
}
}
System.out.println();// a new line just after printing *s
}

Starting loops with 1 can sometimes help you visualize better.
int stopAt = 7;
for (int i = 1; i <= stopAt ; i += 2) {
for (int j = 1; j <= stopAt; j++) {
System.out.print(j <= stopAt - i ? " " : "*");
}
System.out.println();
}
Notice, how each row prints an odd number of *s ending at the line with 7. So, you start with i at 1 and go through 3 1+2, 5 3+2, and then stopAt 7 5+2.
The nested for loop has to print 7 characters always to make sure *s appear right aligned. So, the loop runs from 1 to 7.

Here the complete code:
for(int i = 0; i < 8; i++){
if( i%2 != 0){
for(int x = 0; x < i; x++){
System.out.print("*");
}
}else{
System.out.println();
}
}