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

Iterate 2d array starting the last row

haiztek

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ozan3

haiztek

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ozan3

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Iterate 2d array starting the last row

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