sort an array on maximum occurrences

Question

I'm new to php and I feel that this language has some really good set of sorting functions for arrays

I have an input array below containing the books , readers and price

$input[]=array("Harrypotter","John",50);
$input[]=array("Twilight","John",60);
$input[]=array("Harrypotter","Jack",80);
$input[]=array("Gonegirl","marion",90);
$input[]=array("Gonegirl","test",90);
$input[]=array("Gonegirl","John",90);
$input[]=array("Gonegirl","eliza",90);

I want to sort the array on first field in such a way that the book which repeats more number of times should come first , the expected O/p is something like this

$input[]=array("Gonegirl","marion",90);
$input[]=array("Gonegirl","test",90);
$input[]=array("Gonegirl","John",90);
$input[]=array("Gonegirl","eliza",90);
$input[]=array("Harrypotter","Jack",80);
$input[]=array("Harrypotter","John",50);
$input[]=array("Twilight","John",60);

I'm able to copy the first field in separate array and get the occurrence by using array_count_values and i'm able to get the expected output through array_multi_sort but it sorts only by alphabetical order of the first field .

Any efficient way of arriving at the solution would be helpful !

Rizier123 · Answer 1 · 2014-11-15T19:12:11.217

1

This should work for you:

<?php

    $input = array();

    $input[]=array("Harrypotter","John",50);
    $input[]=array("Twilight","John",60);
    $input[]=array("Harrypotter","Jack",80);
    $input[]=array("Gonegirl","marion",90);
    $input[]=array("Gonegirl","test",90);
    $input[]=array("Gonegirl","John",90);
    $input[]=array("Gonegirl","eliza",90);

    function cmp($a, $b) {
        return strcmp($a[0], $b[0]);
    }

    usort($input, "cmp");

    print_r($input);

?>

edited Nov 15 '14 at 19:12

answered Nov 15 '14 at 18:46

Rizier123

58,877
16
101
156

Why do you compare prices instead of names? – u_mulder Nov 15 '14 at 18:50
@u_mulder Because he wants to order the array by the prices – Rizier123 Nov 15 '14 at 18:51
no it should be on the maximum occurences of first field ie the book name – Santhosh Pai Nov 15 '14 at 18:52
`I want to sort the array on first field` – u_mulder Nov 15 '14 at 18:52
Replace `return strcmp($b[2], $a[2]);` with `return strcmp($a[0], $b[0]);` and done – u_mulder Nov 15 '14 at 19:02

score 1 · Accepted Answer · answered Nov 15 '14 at 19:05

1

You will first have to establish a count of how often each value occurs, then you can write a comparison function that sorts by those values:

$counts = array_count_values(array_map('current', $input));
usort($input, function (array $a, array $b) use ($counts) {
    return $counts[$b[0]] - $counts[$a[0]];
});

answered Nov 15 '14 at 19:05

deceze

510,633
85
743
889

works like a charm tested for different inputs ,but it sorts in the ascending order . What does the call back function do ? – Santhosh Pai Nov 15 '14 at 19:09
See http://stackoverflow.com/a/17364128/476. Just reverse the `$a` and `$b` parameters if you want it the other way around. – deceze Nov 15 '14 at 19:13
@SanthoshPai You wanted to sort it that it ends with 80, 50, 60 and his answer ends with: 50, 80, 60? – Rizier123 Nov 15 '14 at 19:22
Hello @Rizier123 , i actually wanted only for maximum occurences of first field . – Santhosh Pai Nov 15 '14 at 19:26

score 0 · Answer 3 · edited May 23 '17 at 12:27

0

array_multisort(array_map('count', $input), SORT_DESC, $input);

PS: From PHP Sort a multidimensional array by number of items

Update:

array_multisort(array_map(function ($fld) {return $fld[0];}, $input), SORT_ASC, $input);

edited May 23 '17 at 12:27

Community

1
1

answered Nov 15 '14 at 18:50

fortune

3,361
1
20
30

no it still sorts in alphabetical order ,need on maximum number of occurences of first field – Santhosh Pai Nov 15 '14 at 18:54

sort an array on maximum occurrences

3 Answers3