fix: clean up Dockerfile to leverage layer caches and solutions

Author: praisetompane

Dockerfile

@@ -7,7 +7,11 @@ COPY . .
 RUN apt-get update \
     && apt-get install aspell -y
 
-RUN apt-get install python3 -y && apt-get install python3-pip -y && apt-get install pipenv -y && ln -s /usr/bin/python3 /usr/bin/python
+RUN apt-get install python3 -y && \
+    apt-get install python3-pip -y && \
+    apt-get install pipenv -y && \
+    ln -s /usr/bin/python3 /usr/bin/python
+
 RUN apt-get install ghc -y
 
 RUN pipenv sync --system -d

programs_per_computational_model/3_stateful/arrays_and_strings/character_count.py

@@ -0,0 +1,18 @@
+def count_in_order_character_occurence(string_input):
+    char_count = 0
+    char_counts =[]
+    last_char_seen = ""
+    
+    idx = 0
+    while(idx < len(string_input)):
+        last_char_seen = string_input[idx]
+        while(idx < len(string_input) and string_input[idx] == last_char_seen):
+            char_count += 1
+            idx += 1
+        char_counts.append((last_char_seen, char_count))
+        char_count = 0
+    
+    return char_counts
+
+if __name__ == "__main__":
+    assert count_in_order_character_occurence("aaaabbbcca") == [('a', 4), ('b', 3), ('c', 2), ('a', 1)]

programs_per_computational_model/3_stateful/numbers/running_sum.py

@@ -0,0 +1,19 @@
+from typing import List
+"""
+    Analysis:
+        N = number of elements in nums list
+        Time = O(N)
+        Space = O(N) + O(1) = O(N)
+"""
+def running_sum(nums: List[int]) -> List[int]:
+    sums = [0] * len(nums)
+    last_sum = 0
+    for i in range(len(nums)):
+        sums[i] = last_sum + nums[i]
+        """
+        This is the key to O(N) runtime, that is remembering the result of the computation.
+        Making the next computation, the sum of the previous computation + the new value.
+            This is consant time.
+        """
+        last_sum = sums[i]
+    return sums

programs_per_computational_model/3_stateful/numbers/series_sum.py

@@ -0,0 +1,15 @@
+def summingSeries(n):
+    """
+        O(N) solution.
+        This is not good enough, because n can be 10^16, which is too large for a linear time algorith.
+    """
+    series_sum = 0
+    for i in range(1, n + 1):
+        series_sum += i**2 - (i -1)**2
+        print(series_sum)
+    return series_sum%(10**9 + 7)
+
+
+
+if __name__ == "__main__":
+    print(summingSeries(3))

programs_per_computational_model/3_stateful/numbers/test_running_sum.py

@@ -0,0 +1,5 @@
+
+from running_sum import running_sum
+
+def test_running_um():
+    assert running_sum([1,2,3,4]) == [1,3,6,10]

todo.txt

@@ -6,6 +6,16 @@
     - assignments:
     - exams:
 
+- computer programming techniques:
+    - lectures:
+    - readings:
+        - Donald Knuth. 1968. The Art of Computer Programming, Volume 1: Fundamental Algorithms. 1, 2, 3, 4A, and 4B
+        - https://pabloagn.com/blog/10-advanced-programming-techniques/ 
+    - assignments:
+    - exams:
+
+
+
 ============================================================================================================
 - next field template:
     - lectures: