counting_sort.cpp (#7)

Algos/counting_sort.cpp

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+//  algorithm (pseudo code) 
+/*  countingSort(array, size)
+    max - find largest element in array
+    initialize count array with all zeros
+    for j - 0 to size
+    find the total count of each unique element and 
+    store the count at jth index in count array
+    for i - 1 to max
+    find the cumulative sum and store it in count array itself
+    for j - size down to 1
+    restore the elements to array
+    decrease count of each element restored by 1 */
+// Counting sort in C++ programming
+
+#include <iostream>
+using namespace std;
+
+void countSort(int array[], int size) {
+    // providing size of array statically 
+    //one can use dynamic allocation also according to need
+  int outputarray[10];
+  int countarray[10];
+  int max = array[0];
+
+  // largest element 
+  for (int i = 1; i < size; i++) {
+    if (array[i] > max)
+      max = array[i];
+  }
+
+// setting count array elements to "0"
+  for (int i = 0; i <= max; ++i) {
+    countarray[i] = 0;
+  }
+
+ // storing count of each element
+  for (int i = 0; i < size; i++) {
+    countarray[array[i]]++;
+  }
+
+  // Storing the cummulative count of each array
+  for (int i = 1; i <= max; i++) {
+    countarray[i] += countarray[i - 1];
+  }
+
+  // Finding the index of each element of the original array in count array, and
+  // placing the elements in output array
+  for (int i = size - 1; i >= 0; i--) {
+    outputarray[countarray[array[i]] - 1] = array[i];
+    countarray[array[i]]--;
+  }
+
+  // Copying the sorted elements into original array
+  for (int i = 0; i < size; i++) {
+    array[i] = outputarray[i];
+  }
+}
+
+//printing the array
+void print(int array[], int size) {
+  for (int i = 0; i < size; i++)
+    cout << array[i] << " ";
+  cout << endl;
+}
+
+//main code
+int main() {
+    int n =8;
+  int array[]= {8,9,4,2,5,6,7,6};
+  countSort(array, n);
+  print(array, n);
+  return 0;
+}