How to Count Occurrence of Duplicate Items in Array

How do I count occurrence of duplicate items in array

array_count_values, enjoy :-)

$array = array(12,43,66,21,56,43,43,78,78,100,43,43,43,21);
$vals = array_count_values($array);
echo 'No. of NON Duplicate Items: '.count($vals).'<br><br>';
print_r($vals);

Result:

No. of NON Duplicate Items: 7
Array
(
    [12] => 1
    [43] => 6
    [66] => 1
    [21] => 2
    [56] => 1
    [78] => 2
    [100] => 1
)

How to count duplicate value in an array in javascript

function count() {    array_elements = ["a", "b", "c", "d", "e", "a", "b", "c", "f", "g", "h", "h", "h", "e", "a"];
    array_elements.sort();
    var current = null;    var cnt = 0;    for (var i = 0; i < array_elements.length; i++) {        if (array_elements[i] != current) {            if (cnt > 0) {                document.write(current + ' comes --> ' + cnt + ' times<br>');            }            current = array_elements[i];            cnt = 1;        } else {            cnt++;        }    }    if (cnt > 0) {        document.write(current + ' comes --> ' + cnt + ' times');    }
}
count();

How to count occurrences of duplicates in array using binary search in C?

You can not use binary search to locate data in unsorted array. The elements must be in increasing order for the binary search work. You can use 'qsort' to sort the array in the program, or modify the input to be sorted.

If you modify the input array to: [1 4 5 5 7] , the output will be: 2

Swift 4 - How to return a count of duplicate values from an array?

You can enumerate through the array and add the values to the dictionary.

var array: [CGFloat] =  [65.0, 65.0, 65.0, 55.5, 55.5, 30.25, 30.25, 27.5]
var dictionary = [CGFloat: Int]()

for item in array {
   dictionary[item] = dictionary[item] ?? 0 + 1
}

print(dictionary)

or you can do foreach on array:

array.forEach { (item) in
  dictionary[item] = dictionary[item] ?? 0 + 1
}

print(dictionary)

or as @rmaddy said:

var set: NSCountedSet =  [65.0, 65.0, 65.0, 55.5, 55.5, 30.25, 30.25, 27.5]
var dictionary = [Float: Int]()
set.forEach { (item) in
  dictionary[item as! Float] = set.count(for: item)
}

print(dictionary)

How to count duplicate elements in ArrayList?

List<String> list = new ArrayList<String>();
    list.add("a");
    list.add("b");
    list.add("c");
    list.add("a");
    list.add("a");
    list.add("a");

int countA=Collections.frequency(list, "a");
int countB=Collections.frequency(list, "b");
int countC=Collections.frequency(list, "c");

count of duplicate elements in an array in php

You can adopt this trick; map each item of the array (which is an array itself) to its respective ['lid'] member and then use array_count_value() to do the counting for you.

array_count_values(array_map(function($item) {
    return $item['lid'];
}, $arr);

Plus, it's a one-liner, thus adding to elite hacker status.

Update

Since 5.5 you can shorten it to:

array_count_values(array_column($arr, 'lid'));

Count duplicates within an Array of Objects

For example:

counter = {}

yourArray.forEach(function(obj) {
    var key = JSON.stringify(obj)
    counter[key] = (counter[key] || 0) + 1
})

Docs: Array.forEach, JSON.stringify.