使用for循环在C ++中打印矩阵辅助对角线？

Question

I have a simple program in which I want to print all of the elements in the secondary diagonal of the matrix - these are the numbers 5,9,13,-21,12 but the program does not work as expected. What am I doing wrong?

#include <iostream>
#define SIZE 5
int a[SIZE][SIZE]={
{1,2,3,4,5},
{6,7,8,9,10},
{11,12,13,14,15},
{100,-21,-70,345,77},
{12,17,765,98,55}
};

for(int i=0;i<5;i++)//The first index increases
for(int k=5;k>0;k--)//The second index decreases
cout<<a[i][k]<<endl;//Printing the element

Answer 1

There is no need for a second for loop . You can do it using only one:

for (int i = 0; i < SIZE; i++){
    std::cout << a[i][SIZE - i - 1] << ' ';
}

This way you have two indexes going opposite ways using a single for loop.

Answer 2

Well, you did

for (k=5; k>0; k--)

but there is no a[0][5]

the last element in the first row is a[0][4] so your array should start from 4 and go down to 0

for (k=4; k>=0; k--)

Btw it can be done with just 1 loop.

For every element of the second diagonal, the sum of the indexes is 4.

0+4=4
1+3=4
2+2=3
3+1=4
4+0=4

so you can write it as a[i][4-i]

for(i=0; i<5; i++) 
cout<<a[i][4-i]<<endl;

Answer 3

Try doing in this way:

for(int i=0; i<5; i++) {
    cout << a[i][4-i] << endl;
}