Lecture 3

SoSe24/lec03_sort_alg/quick_plot.py

@@ -6,8 +6,8 @@ import quick_sort as qs
 
 
 if __name__ == "__main__":
-    filename = "../../seq3.txt"
-    dummy = read_int_sequence("../../seq3.txt")
+    filename = "../../seq3_sorted.txt"
+    dummy = read_int_sequence(filename)
     n = len(dummy)
     step = n // 100
 

SoSe24/lec03_sort_alg/quick_sort.py

@@ -21,16 +21,45 @@ def partition(z: AlgoDatArray, left: int, right: int) -> int:
         z[i], z[right] = z[right], z[i]
     return i
 
+def median_pivot(z: AlgoDatArray, left: int, right: int) -> int:
+    mid = left + (right - left) // 2
+    if z[left] < z[right]:
+        if z[mid] < z[right]:
+            # right is the largest
+            if z[mid] < z[left]:
+                # left is in the middle
+                z[left], z[right] = z[right], z[left]
+            else:
+                # mid is in the middle
+                z[mid], z[right] = z[right], z[mid]
+        else:
+            # right is in the middle
+            pass
+    else:
+        if z[mid] < z[right]:
+            # right is in the middle
+            pass
+        else:
+            #right is the smallest
+            if z[mid] < z[left]:
+                # mid is in the middle
+                z[mid], z[right] = z[right], z[mid]
+            else:
+                # mid is in the middle
+                z[left], z[right] = z[right], z[left]
+    return partition(z, left, right)
+
 def quick_sort(z: AlgoDatArray, left: int, right: int):
     if left < right:
         q = partition(z, left, right)
+        #q = median_pivot(z, left, right)
         quick_sort(z, left, q-1)
         quick_sort(z, q+1, right)
 
 pivot = AlgoDatValue(0)
 
 if __name__ == "__main__":
-    z = read_int_sequence("../../seq0.txt")
+    z = read_int_sequence("../../seq3.txt")
     print(z, len(z))
     start = pfc()
     quick_sort(z, 0, z.size-1)