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();
Finding number of repeated elements in an array using C
To avoid over-counting, you will need to keep track of which numbers have already been repeated. I wold just have a second array to save "already repeated" values:
#include <stdio.h>
int main()
{
int n, p = 0, r = 0;
printf("Enter the size of the array: ");
scanf(" %u",&n);
int arr[n];
int rep[n - 1];
for (int i = 0; i < n; i++) {
printf("Enter arr[%d]: ",i);
scanf(" %d",&arr[i]);
}
for (int i = 0; i < n; i++) {
int count = 1, j;
for (j = 0; j < r; j++) {
if (arr[i] == rep[j])
break;
}
if (j < r)
continue;
for (j = i + 1; j < n; j++)
if (arr[i] == arr[j])
count++;
if (count > 1) {
p = p + count;
rep[r++] = arr[i];
}
}
printf("Number of repitions is %d\n",p);
}
Count the number of times a same value appears in a javascript array
There might be different approaches for such purpose.
And your approach with for
loop is obviously not misplaced(except that it looks redundantly by amount of code).
Here is some additional approaches to get the occurrence of a certain value in array:
Using
Array.forEach
method:var arr = [2, 3, 1, 3, 4, 5, 3, 1];
function getOccurrence(array, value) {
var count = 0;
array.forEach((v) => (v === value && count++));
return count;
}
console.log(getOccurrence(arr, 1)); // 2
console.log(getOccurrence(arr, 3)); // 3Using
Array.filter
method:function getOccurrence(array, value) {
return array.filter((v) => (v === value)).length;
}
console.log(getOccurrence(arr, 1)); // 2
console.log(getOccurrence(arr, 3)); // 3
How do I count occurrence of duplicate items in array [duplicate]
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
)
Counting the occurrences / frequency of array elements
const arr = [2, 2, 5, 2, 2, 2, 4, 5, 5, 9];
function foo (array) {
let a = [],
b = [],
arr = [...array], // clone array so we don't change the original when using .sort()
prev;
arr.sort();
for (let element of arr) {
if (element !== prev) {
a.push(element);
b.push(1);
}
else ++b[b.length - 1];
prev = element;
}
return [a, b];
}
const result = foo(arr);
console.log('[' + result[0] + ']','[' + result[1] + ']')
console.log(arr)
Counting repeated elements in an integer array
This kind of problems can be easy solved by dictionaries (HashMap in Java).
// The solution itself
HashMap<Integer, Integer> repetitions = new HashMap<Integer, Integer>();
for (int i = 0; i < crr_array.length; ++i) {
int item = crr_array[i];
if (repetitions.containsKey(item))
repetitions.put(item, repetitions.get(item) + 1);
else
repetitions.put(item, 1);
}
// Now let's print the repetitions out
StringBuilder sb = new StringBuilder();
int overAllCount = 0;
for (Map.Entry<Integer, Integer> e : repetitions.entrySet()) {
if (e.getValue() > 1) {
overAllCount += 1;
sb.append("\n");
sb.append(e.getKey());
sb.append(": ");
sb.append(e.getValue());
sb.append(" times");
}
}
if (overAllCount > 0) {
sb.insert(0, " repeated numbers:");
sb.insert(0, overAllCount);
sb.insert(0, "There are ");
}
System.out.print(sb.toString());
Python: count repeated elements in the list
You can do that using count
:
my_dict = {i:MyList.count(i) for i in MyList}
>>> print my_dict #or print(my_dict) in python-3.x
{'a': 3, 'c': 3, 'b': 1}
Or using collections.Counter
:
from collections import Counter
a = dict(Counter(MyList))
>>> print a #or print(a) in python-3.x
{'a': 3, 'c': 3, 'b': 1}
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