extract unique rows of 2d array

[haiqi]

hi,

i have a 2d array with entries like

1.2 2.3

2.4 4.5

1.2 2.3

1.9 3.5


I want to extract all the unique rows of the 2d array like this

1.2 2.3

2.4 4.5

1.9 3.5



Any suggestions on how I can do this?

Thanks

[Stalker]

The easiest way I think is to store the unique rows in an another array. That way you can compare to see if the row is unique or not.

[naaissus]

My English isn't good enough but I will try to explain what I was trying to accomplish.
So, for each row (r1) I will cycle down the rows to see if there is a row (r2) that is completely same as the r1. If that is the case, I will add index of r2 to my list of no-no indexes. Then, I will copy all rows from original array to the result array, except rows that are in my no-no list.
It looks like my code works, but I'm not sure :D
You didn't mention - C or C++? As you can C, my code is written in C.

#include <stdio.h>
#define MAX 50
int main() {
    int rows, cols;
    float arr[MAX][MAX];

    printf("No. of rows: "); scanf("%d", &rows);
    printf("No. of cols: "); scanf("%d", &cols);
    printf("\n");

    for (int i = 0; i < rows; i++)
        for (int j = 0; j < cols; j++)
            scanf("%f", &arr[i][j]);

    int nonolist[MAX],
        count = 0;
    for (int r1 = 0; r1 < rows; r1++) {
        for (int r2 = r1 + 1; r2 < rows; r2++) {
            bool same = false;
            for (int c = 0; c < cols; c++) {
                if (arr[r2][c] == arr[r1][c])
                    same = true;
                else {
                    same = false;
                    break;
                }
            }
            if (same) {
                nonolist[count] = r2;
                count++;
            }
        }
    }

    printf("\n");
    for (int i = 0; i < count; i++)
        printf("%d ", nonolist[i]);
    printf("\n\n");

    float result[MAX][MAX];
    int rows1 = 0;
    for (int r = 0; r < rows; r++) {
        bool nono = false;
        for (int i = 0; i < count; i++) {
            if (nonolist[i] == r) {
                nono = true;
                break;
            }
        }
        if (nono) continue;
        for (int c = 0; c < cols; c++) {
            result[rows1][c] = arr[r][c];
            printf("%.1f ", result[rows1][c]);
        }
        printf("\n");
        rows1++;
    }
    return 0;
}

[keskiverto]

If you had the 2D array stored as a std::vector of vectors (each row as one std::vector) then you could use the relational operators of the std::vector
http://www.cplusplus.com/reference/vector/vector/operators/

However, your values are floating point values and the equality comparison of floating points is tricky. Therefore, the use of std::equal with appropriate custom binary predicate is recommended.