add snippets

Author: Levelent

week6/snippets/0_rec_basic.py

@@ -0,0 +1,14 @@
+# Calculates 1 + 2 + ... + n, recursively
+def sum_of_first(n: int):
+    # Base Case
+    if n == 0:
+        return 0
+    
+    # Recursive Step
+    return n + sum_of_first(n-1)
+
+print(sum_of_first(4))
+
+# Try 7, 0, -1, 100, 10000
+# Replace + with *, Try 4
+# Fix?

week6/snippets/1_fib_rec.py

@@ -0,0 +1,11 @@
+def fib(n: int) -> int:
+    if n < 0:
+        raise ValueError("Not Defined")
+    if n == 0 or n == 1:
+        return n
+    
+    return fib(n-1) + fib(n-2)
+
+print(fib(4))
+print(fib(20))
+print(fib(50))  # Why?

week6/snippets/2_fib_lin.py

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+def fib_linear(n: int) -> int:
+    if n < 0:
+        raise ValueError("Not Defined")
+    if n in [0, 1]:
+        return n
+    
+    prev = 0
+    curr = 1
+    for _ in range(n-1):
+        new = prev + curr
+        prev = curr
+        curr = new
+    return curr
+
+print(fib_linear(50))
+print(fib_linear(100))

week6/snippets/3_fib_dict.py

@@ -0,0 +1,16 @@
+seen = {}
+
+def fib_dict(n: int) -> int:
+    if n <= 1:
+        return n
+    
+    # Lookup or recurse
+    prev1 = seen[n-1] if n-1 in seen else fib_dict(n-1)
+    prev2 = seen[n-2] if n-2 in seen else fib_dict(n-2)
+
+    # Add to lookup when found
+    seen[n] = prev1 + prev2
+    return seen[n]
+
+print(fib_dict(50))
+print(fib_dict(100))

week6/snippets/4_fib_cache.py

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+from functools import cache
+
+@cache
+def fib_cache(n: int) -> int:
+    if n <= 1:
+        return n
+    return fib_cache(n-1) + fib_cache(n-2)
+
+print(fib_cache(50))
+print(fib_cache(100))

week6/snippets/5_game.py

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+# Guessing game
+from random import randint
+from time import sleep
+
+answer = randint(1, 1000)  # My random number
+
+attempts = 0
+guess = 0
+while True:
+    sleep(0.2)
+
+    guess = input("Guess a number between 1 and 1000: ")
+    if not guess.isdigit() or int(guess) < 1 or int(guess) > 1000:
+        continue
+
+    attempts += 1
+    if int(guess) > answer:
+        print(f"{guess} is too high...")
+    elif int(guess) < answer:
+        print(f"{guess} is too low...")
+    else:
+        break
+
+print(f"Correct! The number was {guess}.")
+print(f"This took you {attempts} attempts.")

week6/snippets/6_bin_search.py

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+def find(items, target) -> bool:
+    return search(items, target, 0, len(items) - 1)
+
+def search(items, target, low, high) -> bool:
+    if low > high:  # Guessed everywhere possible
+        return False
+    
+    mid = (low + high) // 2  # Make a guess in the middle
+    
+    if items[mid] > target:  # Guess too high
+        return search(items, target, low, mid - 1)
+    elif items[mid] < target:   # Guess too low
+        return search(items, target, mid + 1, high)
+    else:  # Got it!
+        return True
+
+# Only works on lists in order (in this case, alphabetical).
+fruits = ["Apple", "Banana", "Cherry", "Durian", "Fig", "Grapefruit", "Orange", "Peach", "Pear", "Pineapple"]
+
+print(find(fruits, "Pear"))
+print(find(fruits, "Chocolate"))
+print(find(fruits, "Z"))

week6/snippets/7_big_o.py

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+# The size of nums affects the time things take to run.
+nums = [75, -63, 39, -88, 83, -7, 12, -99, 83, 29, -43, -33, -74, -76, -21, -100, 26, 97, 37, -61]
+target = 14
+found = False
+
+# Determines if any two distinct numbers in the list add up to the target
+for i in range(len(nums)):
+    for j in range(len(nums)):
+        if nums[i] + nums[j] == target and i != j:
+            found = True
+
+print(":)") if found else print(":(")
+
+# In this case, len(nums) = 20. The inner loop executes 20^2 = 400 times.
+# Is this a good algorithm?

week6/snippets/8_sort_bubble.py

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+
+def in_order(some_list):
+    for i in range(len(some_list)-1):
+        if some_list[i] > some_list[i+1]:
+            return False
+    return True
+
+def bubble(some_list):
+    flag = False
+    while not flag:
+        flag = True
+        for i in range(len(some_list) - 1):
+            # Not in order
+            if some_list[i] > some_list[i+1]:
+                flag = False
+                # Swap the two elements
+                temp = some_list[i]
+                some_list[i] = some_list[i+1]
+                some_list[i+1] = temp
+
+nums = [2, 3, 4, 10, 6, 1, 8, 9, 5, 11, 12, 7]
+bubble(nums)
+print(nums)

week6/snippets/9_sort_bogo.py

@@ -0,0 +1,15 @@
+from random import shuffle
+
+def in_order(some_list):
+    for i in range(len(some_list)-1):
+        if some_list[i] > some_list[i+1]:
+            return False
+    return True
+
+def bogosort(some_list):
+    while not in_order(some_list):
+        shuffle(some_list)
+
+nums = [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1]
+bogosort(nums)
+print(nums)