import java.util.Arrays;
/**
Create a sorted unique array (arr) from a matrix (arr of arr).
Steps:
1. Flatten matrix into arr
2. Sort arr (Arrays.sort)
3. Remove duplicates in-place
*/
public class SortedUniqueArrFromMatrix {
// Flatten + sort + unique
static int[] makeSortedUniqueArr(int[][] mat) {
int rows = mat.length;
int cols = mat[0].length;
int total = rows * cols;
// Allocate arr large enough for all elements
int[] arr = new int[total];
// Flatten matrix into arr
int k = 0;
for (int[] slc : mat) { // slc = slice (row)
for (int x : slc) {
arr[k++] = x;
}
}
// Sort arr
Arrays.sort(arr);
// Remove duplicates in-place
int u = 0;
for (int i = 0; i < total; i++) {
if (i == 0 || arr[i] != arr[i - 1]) {
arr[u++] = arr[i];
}
}
// Return arr resized to unique count
return Arrays.copyOf(arr, u);
}
public static void main(String[] args) {
int[][] mat = {
{5, 1, 17, 3, 8, 2, 1, 9},
{3, 5, 7, 4, 2, 3, 4, 1},
{9, 1, 8, 2, 3, 88, 17, 5}
};
int[] arr = makeSortedUniqueArr(mat);
for (int x : arr) {
System.out.print(x + " ");
}
}
}
/*
run:
1 2 3 4 5 7 8 9 17 88
*/
