Faster random number list generation

column1/problem4.py

@@ -1,14 +1,21 @@
 import random
 
 def k_uniq_rand_nums_of_n(n, k):
-    nums = [0]
-    for i in xrange(1, n):
-        nums.append(i)
+    nums = [0] * n
+    for i in xrange(n - 1, n - 1 - k, -1):
         j = random.randint(0, i)
-        nums[i] = nums[j]
-        nums[j] = i
 
-    return nums[:k]
+        num_j = nums[j] 
+        if num_j == 0:
+            num_j = j + 1
+
+        num_i = nums[i] 
+        if num_i == 0:
+            num_i = i + 1
+
+        nums[i], nums[j] = num_j, num_i
+
+    return nums[-k:]
 
 if __name__ == '__main__':
     import sys

column1/test.sh

@@ -1,9 +1,9 @@
-echo "Generating input"
+echo `date +%T` "Generating input"
 python problem4.py $1 $2 > input
-echo "Generating output"
+echo `date +%T` "Generating output"
 cat input | python problem3.py $1 > output
-echo "Sorting input"
+echo `date +%T` "Sorting input"
 sort -g input > input_sorted
-echo "Diffing sorted input and output"
+echo `date +%T` "Diffing sorted input and output"
 diff -s input_sorted output
 rm input input_sorted output