- You will write three static methods, all of which are in a single enclosing class, named DiverseArray.
- The first method returns the sum of the values of a one-dimensional array
- The second method returns an array that represents the sums of the rows of a two-dimensional array
- The third method analyzes row sums.
(a) Write a static method arraySum that calculates and returns the sum of the entries in a specified one-dimensional array. The following example shows an array arr1 and the value returned by a call to arraySum.
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| //create an array of integers
int[] arr1 = {1, 3, 2, 7, 3};
public static int arraySum (int [ ] arr){
//calculate sum of array
int sum = 0;
for (int i : arr) {
sum += i;
}
//return sum of array
return sum;
}
arraySum(arr1)
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(b) Write a static method rowSums that calculates the sums of each of the rows in a given two-dimensional array and returns these sums in a one-dimensional array. The method has one parameter, a two-dimensional array arr2D of int values. The array is in row-major order: arr2D [ r ] [ c ] is the entry at row r and column c. The method returns a one-dimensional array with one entry for each row of arr2D such that each entry is the sum of the corresponding row in arr2D.
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| //initial 2D array for my own testing
int[][] mat1 = { { 1, 3, 2, 8, 3 }, { 10, 10, 4, 6, 2 }, { 5, 3, 5, 9, 6 }, { 7, 6, 4, 2, 1 }};
public static int[] rowSums (int [][] arr2D) {
//create initial array
int [] arrSums = new int[arr2D.length];
//calculate sum of each row in 2d array
int rowNum = 0;
for (int[] row : arr2D) {
//call part a function to calculate sum of each row (1D arrays)
arrSums[rowNum] = arraySum(row);
//System.out.println(Arrays.toString(arrSums));
rowNum++;
}
//return new array of row sums
return arrSums;
}
int[] rowSumsResult = rowSums(mat1);
System.out.println("Row Sums: " + Arrays.toString(rowSumsResult));
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| Row Sums: [17, 32, 28, 20]
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(c) Write a static method isDiverse that determines whether or not a given two-dimensional array is diverse. The method has one parameter: a two-dimensional array arr2D of int values. The method should return true if all the row sums in the given array are unique; otherwise, it should return false. In the arrays shown above, the call isDiverse (mat1) returns true and the call isDiverse(mat2) returns false.
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| public static boolean isDiverse(int [][] arr2D) {
//call function in part b
int[] rowSumsResult = rowSums(mat1);
//iterate through for each row sum
for (int i = 0; i < rowSumsResult.length; i++) {
//iterate through array for each sum but to compare this time. starts at the second item in the list
for (int j = i + 1 ; j < rowSumsResult.length; j++) {
if (rowSumsResult[i] == rowSumsResult[j]) {
return false;
}
}
}
return true;
}
isDiverse(mat1);
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