Counting Sort

For each input element, determine the number of elements smaller than it. Based on this information, place the input element directly into its correct position.
::: code-tabs
@tab Java

public class CountingSort implements IArraySort {
    @Override
    public int[] sort(int[] sourceArray) throws Exception {
        // Copy arr to avoid modifying the original parameter content
        int[] arr = Arrays.copyOf(sourceArray, sourceArray.length);
        int maxValue = getMaxValue(arr);
        return countingSort(arr, maxValue);
    }
    private int[] countingSort(int[] arr, int maxValue) {
        int bucketLen = maxValue + 1;
        int[] bucket = new int[bucketLen];
        for (int value : arr) {
            bucket[value]++;
        }
        int sortedIndex = 0;
        for (int j = 0; j < bucketLen; j++) {
            while (bucket[j] > 0) {
                arr[sortedIndex++] = j;
                bucket[j]--;
            }
        }
        return arr;
    }
    private int getMaxValue(int[] arr) {
        int maxValue = arr[0];
        for (int value : arr) {
            if (maxValue < value) {
                maxValue = value;
            }
        }
        return maxValue;
    }
}

@tab JavaScript

function countingSort(arr, maxValue) {
    var bucket = new Array(maxValue+1),
        sortedIndex = 0,
        arrLen = arr.length,
        bucketLen = maxValue + 1;
    for (var i = 0; i < arrLen; i++) {
        if (!bucket[arr[i]]) {
            bucket[arr[i]] = 0;
        }
        bucket[arr[i]]++;
    }
    for (var j = 0; j < bucketLen; j++) {
        while(bucket[j] > 0) {
            arr[sortedIndex++] = j;
            bucket[j]--;
        }
    }
    return arr;
}

@tab Python

def countingSort(arr, maxValue):
    bucketLen = maxValue+1
    bucket = [0]*bucketLen
    sortedIndex = 0
    arrLen = len(arr)
    for i in range(arrLen):
        if not bucket[arr[i]]:
            bucket[arr[i]]=0
        bucket[arr[i]]+=1
    for j in range(bucketLen):
        while bucket[j]>0:
            arr[sortedIndex] = j
            sortedIndex+=1
            bucket[j]-=1
    return arr

@tab Go

func countingSort(arr []int, maxValue int) []int {
    bucketLen := maxValue + 1
    bucket := make([]int, bucketLen) // Initialize array with zeros
    sortedIndex := 0
    length := len(arr)
    for i := 0; i < length; i++ {
        bucket[arr[i]] += 1
    }
    for j := 0; j < bucketLen; j++ {
        for bucket[j] > 0 {
            arr[sortedIndex] = j
            sortedIndex += 1
            bucket[j] -= 1
        }
    }
    return arr
}

@tab PHP

function countingSort($arr, $maxValue = null)
{
    if ($maxValue === null) {
        $maxValue = max($arr);
    }
    for ($m = 0; $m < $maxValue + 1; $m++) {
        $bucket[] = null;
    }
    $arrLen = count($arr);
    for ($i = 0; $i < $arrLen; $i++) {
        if (!array_key_exists($arr[$i], $bucket)) {
            $bucket[$arr[$i]] = 0;
        }
        $bucket[$arr[$i]]++;
    }
    $sortedIndex = 0;
    foreach ($bucket as $key => $len) {
        if($len !== null){
            for($j = 0; $j < $len; $j++){
                $arr[$sortedIndex++] = $key;
            }
        }
    }
    return $arr;
}

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