Iterate 2d array starting the last row

haiztek · 5 Nis 2021

How can I iterate a 2d array starting the last row? I've been trying a lot lately but I didn't find the solution, even google and stack overflow didn't gave me enough clues.
Here is my Sample code

C++:

String[][] array = {
    {"a", "b", "c"},
    {"d", "e"} // here at array[1][0] I want here to start the loop iteration
};
for (int row = 0; row < array.length; row++) {
    for (int col = 0; col < array[x].length; col++) {
        // do_Something
    }
}

Should I change the row from int row = 0 to int row = -1?
for row = -1; row < array.length; row++?

ozan3 · 5 Nis 2021

You can reverse it.

Straight one :

C++:

#include <iostream>
using namespace std;

int main() {
    int test[3][2] = {{2, -5},
                      {4, 0},
                      {9, 1}};

    // use of nested for loop
    // access rows of the array
    for (int i = 0; i < 3; ++i) {

        // access columns of the array
        for (int j = 0; j < 2; ++j) {
            cout << "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}

Reverse one :

C++:

#include <iostream>
using namespace std;

int main() {
    int test[3][2] = {{2, -5},
                      {4, 0},
                      {9, 1}};

    // use of nested for loop
    // access rows of the array
    for (int i = 2; i > -1; i--) {

        // access columns of the array
        for (int j = 1; j > -1; j--) {
            cout << "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}

Edit this method for yourself :

C++:

#include<iostream>

#include<conio.h>
using namespace std;

 main() {
    //clear the screen.
 
    //declare variable type int
    int a[3][3], i, j;
    //Input the numbers
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            cout << "Enter number :";
            cin >> a[i][j];
        }
    }
    //display the matrix
    for (i = 2; i >= 0; i--) {
        for (j = 2; j >= 0; j--) {
            cout << a[i][j] << "\t";
        }
        cout << endl;
    }
    return 0;
}

haiztek · 6 Nis 2021

ozan3' Alıntı:

You can reverse it.

Straight one :

C++:

#include <iostream>
using namespace std;

int main() {
    int test[3][2] = {{2, -5},
                      {4, 0},
                      {9, 1}};

    // use of nested for loop
    // access rows of the array
    for (int i = 0; i < 3; ++i) {

        // access columns of the array
        for (int j = 0; j < 2; ++j) {
            cout << "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}

Reverse one :

C++:

#include <iostream>
using namespace std;

int main() {
    int test[3][2] = {{2, -5},
                      {4, 0},
                      {9, 1}};

    // use of nested for loop
    // access rows of the array
    for (int i = 2; i > -1; i--) {

        // access columns of the array
        for (int j = 1; j > -1; j--) {
            cout << "test[" << i << "][" << j << "] = " << test[i][j] << endl;
        }
    }

    return 0;
}

Edit this method for yourself :

C++:

#include<iostream>

#include<conio.h>
using namespace std;

main() {
    //clear the screen.

    //declare variable type int
    int a[3][3], i, j;
    //Input the numbers
    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            cout << "Enter number :";
            cin >> a[i][j];
        }
    }
    //display the matrix
    for (i = 2; i >= 0; i--) {
        for (j = 2; j >= 0; j--) {
            cout << a[i][j] << "\t";
        }
        cout << endl;
    }
    return 0;
}

Ohh yes, it was just in the condition. I can also do like for (int i = arr.lenght - 1; i != -1; i--) which can be start at the end of the row of 2d array. Anyways, thnx for the suggestion, I could use your idea to apply it to my code.

ozan3 · 6 Nis 2021

haiztek' Alıntı:
Ohh yes, it was just in the condition. I can also do like for (int i = arr.lenght - 1; i != -1; i--) which can be start at the end of the row of 2d array. Anyways, thnx for the suggestion, I could use your idea to apply it to my code.

And thanks for your solution. İt seems better than mine

Ara

Iterate 2d array starting the last row

haiztek

no value

ozan3

haiztek

no value

ozan3

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