sorting: add pigeonhole sorting

Author: notakbuzz

Sorting/PigeonholeSort.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+void pigeonholeSort(int arr[], int n)
+{
+	int min = arr[0], max = arr[0];
+	for (int i = 1; i < n; i++)
+	{
+		if (arr[i] < min)
+			min = arr[i];
+		if (arr[i] > max)
+			max = arr[i];
+	}
+	int range = max - min + 1; // Find range
+
+	vector<int> holes[range];
+
+	for (int i = 0; i < n; i++)
+		holes[arr[i]-min].push_back(arr[i]);
+
+	int index = 0; // index in sorted array
+	for (int i = 0; i < range; i++)
+	{
+	vector<int>::iterator it;
+	for (it = holes[i].begin(); it != holes[i].end(); ++it)
+			arr[index++] = *it;
+	}
+}
+
+int main()
+{
+	int arr[] = {8, 3, 2, 7, 4, 6, 8};
+	int n = sizeof(arr)/sizeof(arr[0]);
+
+	pigeonholeSort(arr, n);
+
+	printf("Sorted order is : ");
+	for (int i = 0; i < n; i++)
+		printf("%d ", arr[i]);
+
+	return 0;
+}