英文:
How to organize columns of 2D array based on sum of columns?
问题
我想要按每列的和降序排列一个2D数组。例如：
列1的总和是10，列2的总和是11，列3的总和是8。需要将列2和列1按降序排序。更新后的2D数组如下：
这是我用来获取每列总和的代码：
我目前还没有对每列的tempSum进行任何操作。希望能提供一些指导。
英文:
I would like to organize a 2D array in descending order of each columns sum. For example:
3 1 12 6 55 4 2
The sum of column 1 would be 10, column 2 would be 11, column 3 would be 8. Columns 2 and 1 would need to switch to be sorted in descending order. The updated 2D array would be:
1 3 16 2 54 5 2
I'm aware of Collections.reverseOrder(), but that only works on sorting 1D arrays in descending order.
Here is the code I am using to get the sum of each column:
int tempSum = 0;for (int i = 0; i < columns; i++) {for (int j = 0; j < rows; j++) {tempSum = array[i][j]}//reset tempSumtempSum = 0;}
I am currently not doing anything with the tempSum of each column. Any guidance would be great.
答案1
得分: 1
尝试这个。
int[][] transpose(int[][] matrix) {int rows = matrix.length, cols = matrix[0].length;int[][] transposed = new int[cols][rows];for (int r = 0; r < rows; ++r)for (int c = 0; c < cols; ++c)transposed[c][r] = matrix[r][c];return transposed;}int[][] m = {{3, 1, 1, 9},{2, 6, 5, 4},{5, 4, 2, 6}};m = transpose(m);Arrays.sort(m, Collections.reverseOrder(Comparator.comparingInt(row -> IntStream.of(row).sum())));m = transpose(m);for (int[] row : m)System.out.println("\t" + Arrays.toString(row));
输出
[9, 1, 3, 1][4, 6, 2, 5][6, 4, 5, 2]
或者如果你需要更高的性能：
m = transpose(m);m = Arrays.stream(m).map(row -> new Object() {int sum = IntStream.of(row).sum();int[] origin = row;}).sorted((a, b) -> Integer.compare(b.sum, a.sum)).map(obj -> obj.origin).toArray(int[][]::new);m = transpose(m);
英文:
Try this.
int[][] transpose(int[][] matrix) {int rows = matrix.length, cols = matrix[0].length;int[][] transposed = new int[cols][rows];for (int r = 0; r < rows; ++r)for (int c = 0; c < cols; ++c)transposed[c][r] = matrix[r][c];return transposed;}
And
int[][] m = {{3, 1, 1, 9},{2, 6, 5, 4},{5, 4, 2, 6}};m = transpose(m);Arrays.sort(m, Collections.reverseOrder(Comparator.comparingInt(row -> IntStream.of(row).sum())));m = transpose(m);for (int[] row : m)System.out.println("\t" + Arrays.toString(row));
output
[9, 1, 3, 1][4, 6, 2, 5][6, 4, 5, 2]
Or if you need more performance
m = transpose(m);m = Arrays.stream(m).map(row -> new Object() {int sum = IntStream.of(row).sum();int[] origin = row;}).sorted((a, b) -> Integer.compare(b.sum, a.sum)).map(obj -> obj.origin).toArray(int[][]::new);m = transpose(m);
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