Java counting sort

counting_sort/Java/count_sort.java

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+import java.util.Arrays;
+import java.util.Collections;
+
+class count_sort {
+    /**
+     * Function to get maximum number in an array of integers.
+     * @param arr the array from which maximum number is to be obtained.
+     */
+    static int getMax(int[] arr) {
+        int max = Integer.MIN_VALUE;
+        for (int each_num: arr) {
+            if (each_num > max) {
+                max = each_num;
+            }
+        }
+        return max;
+    }
+
+    static int[] countSort(int[] arr) {
+        /**
+         * Function to sort the arrays based on the Counting sort alogrithm.
+         * This algorithm works by maintaining the count of each number from the array
+         * and then placing it at the right position in the resulting array
+         * @param arr the array to be sorted.
+         */
+        int maximum_number = getMax(arr); // get the max number in the array in order to declare count array.
+        int[] count_arr = new int[maximum_number + 1]; // maximum_number + 1 as we need to correctly
+        //map each index with the number in the array
+
+        for (int i = 0; i < count_arr.length; i++) {
+            count_arr[i] = 0;
+        }
+
+        for (int each_number: arr) {
+            count_arr[each_number] += 1; // get the count of each number in the original array.
+        }
+
+        for (int i = 1; i < count_arr.length; i++) {
+            count_arr[i] += count_arr[i - 1]; // rolling sum gets count of numbers less than current index in the original array
+        }
+
+        int[] sorted_arr = new int[arr.length]; // declare and initialize sorted array.
+        for (int i = 0; i < sorted_arr.length; i++) {
+            sorted_arr[i] = 0;
+        }
+
+        for (int each_num: arr) {
+            sorted_arr[count_arr[each_num] - 1] = each_num; //place the arrays at apt position on the basis of value in count array
+            count_arr[each_num] -= 1;
+        }
+        return sorted_arr;
+    }
+
+    public static void main(String[] args) {
+        int[] array = {
+            4,
+            2,
+            1,
+            55,
+            22,
+            1,
+            77
+        }; // tester code
+        int[] sorted_arr = countSort(array);
+        for (int each_num: sorted_arr) {
+            System.out.print(each_num + " ");
+        }
+    }
+}