How to access elements from a 1-D array using nested loops?

Question

I need to store the following data in a vector (in this order):

cAge[0]  = 'Age (1) (1)';
cAge[1]  = 'Age (1) (2)';
cAge[2]  = 'Age (1) (3)';
cAge[3]  = 'Age (2) (1)';
cAge[4]  = 'Age (2) (2)';
cAge[5]  = 'Age (2) (3)';
cAge[6]  = 'Age (3) (1)';
cAge[7]  = 'Age (3) (2)';
cAge[8]  = 'Age (3) (3)';
cAge[9]  = 'Age (4) (1)';
cAge[10] = 'Age (4) (2)';
cAge[11] = 'Age (4) (3)';

I can do it with a for loop without problems:

var cAge = [];

for (var i=1; i<=4; i++) {
  for (var j=1; j<=3; j++) {
    cAge.push('Age (' + i + ')' + ' ' + '(' + j + ')');
  }
}

However I am not able to show all of them using the following nested loop:

for (var i=1; i<=4; i++) {
  for (var j=1; j<=3; j++) {
    console.log(cAge[j-1]); // <- What should j-1 be?
  }
}

It produces:

Age (1) (1)
Age (1) (2)
Age (1) (3)
Age (1) (1)
Age (1) (2)
Age (1) (3)
Age (1) (1)
Age (1) (2)
Age (1) (3)
Age (1) (1)
Age (1) (2)
Age (1) (3)

What should j-1 be?

You are pushing data in the 1-d array. So just use forEach or for-loop — DecPK
– DecPK, Commented Apr 15, 2021 at 4:49

Som Shekhar Mukherjee · Accepted Answer · 2021-04-15 05:25:11Z

2

Accessing elements from a 1-D array using nested loops:

const cAge = [],
  nrows = 4,
  ncols = 3;

for (var i = 1; i <= nrows; i++) {
  for (var j = 1; j <= ncols; j++) {
    cAge.push("Age (" + i + ")" + " " + "(" + j + ")");
  }
}

for (var i = 0; i < nrows; i++) {
  for (var j = 0; j < ncols; j++) {
    console.log(cAge[i * ncols + j]);
  }
}

Here, ncols = 3

`i` in nested loop	`j` in nested loop	1-D index
0	0	`0 * 3 + 0` = 0
0	1	`0 * 3 + 1` = 1
0	2	`0 * 3 + 2` = 2
1	0	`1 * 3 + 0` = 3
1	1	`1 * 3 + 1` = 4
1	2	`1 * 3 + 2` = 5
2	0	`2 * 3 + 0` = 6
2	1	`2 * 3 + 1` = 7
2	2	`2 * 3 + 2` = 8

edited Apr 15, 2021 at 5:25

answered Apr 15, 2021 at 4:54

Som Shekhar Mukherjee

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1 Comment

Som Shekhar Mukherjee Over a year ago

@manooooh Please check if this solves your problem, let me know if you have any issues.

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