// Challenge by Ravinder Singh located here: // https://www.sololearn.com/Discuss/822439/?ref=app // [CHALLANGE] Pascal Triangle // Input(number of rows) = 6 // output: // 1 // 1 1 // 1 2 1 // 1 3 3 1 // 1 4 6 4 1 // 1 5 10 10 5 1 // Create a program which will make such triangle // 1>Using Arrays // 2>Without using Arrays // Good Luck :) // package pascal; import java.util.Scanner; // ********************* Pascal ******************** // // This is the main class of my pascal package. It // solves and displays Pascal Triangles with 1 to // 10 lines as requested by the user. If the user's // request is invalid, it defaults to 6. This // calculates each line into an array based on the // previous line. public class Pascal { static final int def = 6; // Default lines. // ******************** display ******************** // // This method displays the number. If the number // is zero, display spaces. Otherwise, display // the number as centered as possible in the // column. Note: this only supports numbers less // than 1000 as displaying bigger triangles can't // fit on my screen. // // Arguments // num is the number to display. // // Returns // Nothing. // // Catches // Nothing. // // Exceptions // Nothing. static void display(int num) { if (num == 0) System.out.print(" "); else if (num < 10) System.out.print(" "+num+" "); else if (num < 100) System.out.print(" "+num); else System.out.print(" "+num); } // display // ******************** lines ******************** // // This method prompts for and validates the // user's requested number of lines. // // Arguments // Nothing. // // Returns // An integer for the number of lines requested // by the user or the default, when the input // is invalid. // // Catches // NoSuchElementException for blank lines. // InputMismatchException for bad integer. // // Exceptions // Nothing. static int lines() { // Declare number to return and attempt to read // it catching any exception. int num; try { // Declare the scanner, prompt for & read an // integer, and close scanner. Scanner scan = new Scanner(System.in); System.out.print("Enter a number: "); num = scan.nextInt(); scan.close(); // If number out of range, complain and use // default. if (num < 1 || num > 10) { System.out.println( "Supported range 1 to 10, using "+ def+"!"); num = def; } else System.out.println(); // Catch any exception, complain, and use default. } catch (Exception e) { System.out.println("Invalid number using "+ def+"!"); num = def; } return num; } // lines // ******************** main ******************** // // The main entry point of the Pascal class to // output the lines required for the challenge. // // Arguments // args: An array of strings that is ignored. // // Returns // Nothing. // // Catches // Nothing. // // Exceptions // Nothing. public static void main(String[] args) { // Read however many lines to display, declare // the array, and initialize it to zero. int num = lines(); int arr[][] = new int[num][num]; for (int l = 0; l < num; l++) for (int c = 0; c < num; c++) arr[l][c] = 0; // Fill in the first line. arr[0][num/2] = 1; // For the remaining lines, fill in the array. for (int l = 1; l < num; l++) { // For even lines, fill in the line. if (l%2 == 1) { // For all but the last element, add // the current and next element of the // previous line to get this element. for (int c = 0; c < num-1; c++) arr[l][c] = arr[l-1][c]+arr[l-1][c+1]; // The last element is equal to the last // in the previous line. arr[l][num-1] = arr[l-1][num-1]; // For odd lines, fill in the line. } else { // The first element is equal to the first // in the previous line. arr[l][0] = arr[l-1][0]; // For all the rest of the elements, add // the previous and current element of the // previous line to get this element. for (int c = 1; c < num; c++) arr[l][c] = arr[l-1][c-1]+arr[l-1][c]; } // if } // for // For each line, display the results. for (int l = 0; l < num; l++) { // If an even number of elements to display, // shift over the display to line up. if (l%2 == 1) System.out.print(" "); // For each column of elements, display them. for (int c = 0; c < num; c++) display(arr[l][c]); // Finish the output line. System.out.println(); } // for } // main } // Pascal

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