add pigeon hole sort (#833)

sorts/pigeon_sort.py

@@ -0,0 +1,50 @@
+'''
+    This is an implementation of Pigeon Hole Sort.
+'''
+
+from __future__ import print_function
+
+def pigeon_sort(array):
+    # Manually finds the minimum and maximum of the array.
+    min = array[0]
+    max = array[0]
+
+    for i in range(len(array)):
+        if(array[i] < min): min = array[i]
+        elif(array[i] > max): max = array[i]
+
+    # Compute the variables
+    holes_range = max-min + 1
+    holes = [0 for _ in range(holes_range)]
+    holes_repeat = [0 for _ in range(holes_range)]
+
+    # Make the sorting.
+    for i in range(len(array)):
+        index = array[i] - min
+        if(holes[index] != array[i]):
+            holes[index] = array[i]
+            holes_repeat[index] += 1
+        else: holes_repeat[index] += 1
+
+    # Makes the array back by replacing the numbers.
+    index = 0
+    for i in range(holes_range):
+        while(holes_repeat[i] > 0):
+            array[index] = holes[i]
+            index += 1
+            holes_repeat[i] -= 1
+
+    # Returns the sorted array.
+    return array
+
+if __name__ == '__main__':
+    try:
+        raw_input           # Python2
+    except NameError:
+        raw_input = input   # Python 3
+    
+    user_input = raw_input('Enter numbers separated by comma:\n')
+    unsorted = [int(x) for x in user_input.split(',')]
+    sorted = pigeon_sort(unsorted)
+
+    print(sorted)