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Exercises.java

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+import java.util.Scanner;
+
+public class Exercises {
+
+    /*
+        complete this function to check if the input number is prime or not
+     */
+    public boolean isPrime(long n) {
+        int i;
+        int m = 0;
+        int flag = 0;
+        System.out.println("Enter your number : ");
+        Scanner scanner = new Scanner(System.in);
+        byte number = scanner.nextByte();
+        i = 2;
+        m = number / 2 ;
+        if(number == 0 || number == 1){
+            System.out.println("it is not prime.");
+        }
+        else{
+             while (i <= m) {
+                if (number % i == 0) {
+                    System.out.println("it is not prime.");
+                    flag = 1;
+                    break; 
+                }
+                i++;
+             }
+             if (flag == 0) {
+                System.out.println("it is prime.");
+             }
+        }
+        return false;
+    }
+
+    /*
+        implement an algorithm to find out the index of input number in a fibonacci sequence starting from 0, 1
+        e.g. 0, 1, 1, 2, 3, 5, ...
+        indices start from 0, e.g. 3 is the index 4 of this sequence
+        if the input is not a fibonacci number with description above, return -1
+     */
+    public long fibonacciIndex(long n) {
+        int number;
+        System.out.print("enter your number : ");
+        Scanner scanner = new Scanner(System.in);
+        n = scanner.nextLong();
+        if(n < 0){
+            return -1 ;  // اعدادی که منفی هستند در دنباله ی فیبوناچی وجود ندارند
+        }
+        int a = 0 ;
+        int b = 1;
+        int index = 0 ;
+        while (b < n) {
+            int temp = b ;
+            b = a + b ;
+            a = temp ;
+            index++ ;
+        }
+        return b == n ? index : -1 ;
+    }
+
+    /*
+        you should create a triangle with "*" and return a two-dimensional array of characters based on that
+        the triangle's area is empty, which means some characters should be " "
+
+        example 1, input = 3:
+        *
+        **
+        ***
+
+        example 2, input = 5:
+        *
+        **
+        * *
+        *  *
+        *****
+
+        the output has to be a two-dimensional array of characters, so don't just print the triangle!
+     */
+    public static char[][] generateTriangle(int n) {
+        if (n <= 0) {
+            return new char[0][0] ;
+        }
+        char [][] triangle = new char[n][n];
+        for(int i = 0 ; i < n ; i++){
+            for(int j = 0 ; j < n ; j++){
+                if (j <= i) {
+                    triangle[i][j] = '*';
+                }
+                else{
+                    triangle[i][j] = ' ';
+                }
+            }
+        }
+        return triangle ;
+    }
+    public static void printTriangle(char[][]triangle) {
+        for(char[] row : triangle){
+            for(char c : row){
+                System.out.print(c);
+            }
+            System.out.println();
+        }
+    }
+
+    public static void main(String[] args) {
+        // you can test your code here, but then it should be checked with test cases
+        // start testing 
+        System.out.print("enter your number : ");
+        Scanner scanner = new Scanner(System.in);
+        int number = scanner.nextInt();
+        char[][] trianglenumber = generateTriangle(number);
+        printTriangle(trianglenumber);
+    }
+}