Rename twoDArrayPrograms to RowsCols and fix style

Author: phrdang

src/com/codefortomorrow/intermediate/chapter10/practice/twoDArrayPrograms.java renamed to src/com/codefortomorrow/intermediate/chapter10/practice/RowsCols.java

@@ -1,5 +1,5 @@
 package com.codefortomorrow.intermediate.chapter10.practice;
-
+// TODO break up into multiple problems
 /*
 Fill a 4 X 6 integer array with 24 random values from 7 to 77.
 Print the values in 4 rows of 6 elements.
@@ -24,13 +24,22 @@
 Print the values in 5 rows of 4 elements.
 Use nested loops to fill the values into the array,
 rather than just declaring the values initially.
-*hint*: You can set the values of the first row.
-(You will then need a loop to print the first row
-separately from the rest of the array.)
 */
 
-public class twoDArrayPrograms {
+public class RowsCols {
 	public static void main(String[] args) {
 		// write code here
 	}
+
+	/**
+	 * Returns a random integer
+	 * in the range [min, max]
+	 * @param min  minimum random integer
+	 * @param max  maximum random integer
+	 * @return a random integer in the range
+	 * [min, max]
+	 */
+	public static int randInt(int min, int max) {
+		return min + (int) (Math.random() * ((max - min) + 1));
+	}
 }

src/com/codefortomorrow/intermediate/chapter10/solutions/RowsCols.java

@@ -0,0 +1,130 @@
+package com.codefortomorrow.intermediate.chapter10.solutions;
+
+/*
+Fill a 4 X 6 integer array with 24 random values from 7 to 77.
+Print the values in 4 rows of 6 elements.
+Using the same array, keep track of the sum of all the values in the array.
+Display the sum on its own line under the values.
+Keep track of the maximum and minimum value in the array.
+Display the max and min on the line below the sum.
+
+Fill a 3 X 3 string array so that the values in each row are “*”, “**”, “***”.
+Print the values in 3 rows of 3 elements, each separated by a tab.
+Fill the array in a loop, with a separate variable that will
+keep track of the number of asterisks in each term.
+
+Fill a 5 X 4 integer array according to the following pattern:
+
+4	9	16	25
+8	27	64	125
+16	81	256	625
+32	243	1024	3125
+64	729	4096	15625
+
+Print the values in 5 rows of 4 elements.
+Use nested loops to fill the values into the array,
+rather than just declaring the values initially.
+*hint*: You can set the values of the first row.
+(You will then need a loop to print the first row
+separately from the rest of the array.)
+*/
+
+// TODO explain min and max value
+
+public class RowsCols {
+	public static void main(String[] args) {
+		int[][] a = new int[4][6]; // create 4x6 array
+		int sum = 0; // sum of all elements in array
+		int max = Integer.MIN_VALUE; // max element in array
+		int min = Integer.MAX_VALUE; // min element in array
+
+		// iterate through each element in a
+		for (int row = 0; row < 4; row++) {
+			for (int col = 0; col < 6; col++) {
+				// generate a random number from 7 to 77
+				// and store it in the array
+				a[row][col] = randInt(7, 77);
+
+				// print that element
+				System.out.print(a[row][col] + "\t");
+
+				// keep a running total of all elements
+				sum += a[row][col];
+
+				// update min or max as needed
+				if (a[row][col] < min) {
+					min = a[row][col];
+				}
+					
+				if (a[row][col] > max) {
+					max = a[row][col];
+				}
+			}
+			System.out.println(); // move to next row
+		}
+
+		// display the sum of all elements
+		// and the max and min element
+		System.out.println("Sum: " + sum);
+		System.out.println("Max: " + max);
+		System.out.println("Min: " + min);
+
+		// add some space between arrays
+		System.out.println();
+		System.out.println();
+
+		// create a 3x3 array
+		String[][] b = new String[3][3]; 
+		String asterisks = "*";
+		int numberOfAsterisks = 0;
+
+		// iterate through the 3x3 array
+		for (int row = 0; row < 3; row++) {
+			for (int col = 0; col < 3; col++) {
+				// store the asterisk(s) in the array
+				b[row][col] = asterisks;
+
+				// print the current element
+				System.out.print(b[row][col] + "\t");
+
+				// update total number of asterisks in array
+				numberOfAsterisks += row + 1;
+			}
+			System.out.println(); // move to next row
+			asterisks += "*"; // each row has 1 more asterisk than the last one
+		}
+
+		// print the total number of asterisks in the array
+		System.out.println("Number of asterisks: " + numberOfAsterisks);
+
+		// add some space between arrays
+		System.out.println();
+		System.out.println();
+
+		// create a 5x4 array
+		int[][] c = new int[5][4];
+ 
+		for (int power = 2; power < 7; power++) {
+			for (int base = 2; base < 6; base++) {
+				// assign the correct element based on the pattern
+				c[power - 2][base - 2] = (int) (Math.pow(base, power));
+
+				// print the current element
+				System.out.print(c[power - 2][base - 2] + "\t");
+			}
+			System.out.println(); // move to next row
+		}
+	}
+
+	/**
+	 * Returns a random integer
+	 * in the range [min, max]
+	 * @param min  minimum random integer
+	 * @param max  maximum random integer
+	 * @return a random integer in the range
+	 * [min, max]
+	 */
+	public static int randInt(int min, int max) {
+		return min + (int) (Math.random() * ((max - min) + 1));
+	}
+}