radix__sort.py

sorts/radix__sort.py

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+# Python program for implementation of Radix Sort
+
+# A function to do counting sort of arr[] according to
+# the digit represented by exp.
+def counting_sort(arr, exp1):
+    n = len(arr)
+
+    # The output array elements that will have sorted arr
+    output = [0] * (n)
+
+    # initialize count array as 0
+    count = [0] * (10)
+
+    # Store count of occurrences in count[]
+    for i in range(0, n):
+        index = arr[i] / exp1
+        count[int((index) % 10)] += 1
+
+    # Change count[i] so that count[i] now contains actual
+    # position of this digit in output array
+    for i in range(1, 10):
+        count[i] += count[i - 1]
+
+    # Build the output array
+    i = n - 1
+    while i >= 0:
+        index = arr[i] / exp1
+        output[count[int((index) % 10)] - 1] = arr[i]
+        count[int((index) % 10)] -= 1
+        i -= 1
+
+    # Copying the output array to arr[],
+    # so that arr now contains sorted numbers
+    i = 0
+    for i in range(0, len(arr)):
+        arr[i] = output[i]
+
+
+# Method to do Radix Sort
+def radix_sort(arr):
+    # Find the maximum number to know number of digits
+    max1 = max(arr)
+
+    # Do counting sort for every digit. Note that instead
+    # of passing digit number, exp is passed. exp is 10^i
+    # where i is current digit number
+    exp = 1
+    while max1 // exp > 0:
+        counting_sort(arr, exp)
+        exp *= 10
+
+
+# Driver code to test above
+arr = [170, 45, 75, 90, 802, 24, 2, 66]
+radix_sort(arr)
+
+for i in range(len(arr)):
+    print(arr[i], end=" ")