Lecture 2

SoSe24/algodat/foundation.py

@@ -328,3 +328,13 @@ def read_int_sequence(filename: str) -> AlgoDatArray:
     for i in range(len(l)):
         a[i].value = l[i]
     return a
+
+def read_int_sequence_limited(filename: str, limit: int) -> AlgoDatArray:
+    """Reads a sequence of integers from a file and returns an AlgoDatArray object."""
+    with open(filename, "r") as file:
+        l = list(map(int, file.read().split()))
+    size = min(len(l), limit)
+    a = AlgoDatArray(size)
+    for i in range(size):
+        a[i].value = l[i]
+    return a

SoSe24/lec03_sort_alg/merge_plot.py

@@ -0,0 +1,47 @@
+from SoSe24.algodat.foundation import AlgoDatArray, AlgoDatValue, read_int_sequence, read_int_sequence_limited, MinusInf
+import matplotlib.pyplot as plt
+
+
+def merge_sort(z: AlgoDatArray, storage: AlgoDatArray, left: int, right: int):
+    if left == right:
+        return
+    mid = (left + right) // 2
+    merge_sort(z, storage, left, mid)
+    merge_sort(z, storage, mid+1, right)
+    left_ptr = left
+    right_ptr = mid+1
+    storage_ptr = left
+    while left_ptr <= mid or right_ptr <= right:
+        if left_ptr <= mid and right_ptr <= right:
+            if z[left_ptr] < z[right_ptr]:
+                storage[storage_ptr].value = z[left_ptr].value
+                left_ptr += 1
+                storage_ptr += 1
+            else:
+                storage[storage_ptr].value = z[right_ptr].value
+                right_ptr += 1
+                storage_ptr += 1
+        elif left_ptr <= mid:
+            storage[storage_ptr].value = z[left_ptr].value
+            left_ptr += 1
+            storage_ptr += 1
+        else:
+            storage[storage_ptr].value = z[right_ptr].value
+            right_ptr += 1
+            storage_ptr += 1
+    for i in range(left, right+1):
+        z[i].value = storage[i].value
+
+
+if __name__ == "__main__":
+    filename = "../../seq3.txt"
+    dummy = read_int_sequence("../../seq3.txt")
+    for right_end in range(1, len(dummy), len(dummy)//100):
+        AlgoDatValue.reset()
+        z = read_int_sequence_limited(filename, right_end)
+        storage = AlgoDatArray(z.size)
+        merge_sort(z, storage, 0, right_end-1)
+        plt.plot([right_end], [AlgoDatValue.memory], 'bo')
+        plt.plot([right_end], [AlgoDatValue.compare], 'ro')
+
+    plt.show()

SoSe24/lec03_sort_alg/merge_sort.py

@@ -29,7 +29,7 @@ def merge_sort(z: AlgoDatArray, storage: AlgoDatArray, left: int, right: int):
             storage[storage_ptr].value = z[right_ptr].value
             right_ptr += 1
             storage_ptr += 1
-    for i in range(left, right+1):
+    for i in range(left, right):
         z[i].value = storage[i].value