Merge branch 'master' of https://github.com/ben-xD/leet

Author: StBogdan

README.md

@@ -4,8 +4,23 @@ Exiting Python solutions can be found [officially here](https://github.com/caree
 
 ### Current progress
 - Chapter 1: 9/9
-- Chapter 2: some/8
+- Chapter 2: 6/8
+- Chapter 3: 8/12
+- Chapter 4: 8/8
+- Chapter 5: 1/10
+- Chapter 6: 0/12
+- Chapter 7: 9/14
+- Chapter 8: 0/8
+- Chapter 9: 2/11
 - Chapter 10: 2/11
+- Chapter 11: 0/6
+- Chapter 12: 0/11
+- Chapter 13: 0/8
+- Chapter 14: 0/7
+- Chapter 15: 0/7
+- Chapter 16: 2/26
+- Chapter 17: 4/26
+
 
 ### Schedule
 - Week 1: Chapter 4: Graphs and Trees

chapter_10/p10_11.py

@@ -0,0 +1,17 @@
+from typing import List
+
+def peaks_and_valeys(arr: List[int]) -> List[int]:
+    for i in range(len(arr)-2):
+        # print(f"looking at {arr[i:i+3]}")
+        if arr[i] >= arr[i+1]:
+            if arr[i+2] < arr[i+1]:
+                arr[i+1], arr[i+2] = arr[i+2], arr[i+1]
+        else:
+            if arr[i+1] < arr[i+2]:
+                arr[i+1], arr[i+2] = arr[i+2], arr[i+1]
+    return arr
+
+if __name__ == "__main__":
+    exs = [[1,2,4,5,6,7], [7,6,5,4,3,2,1], [9,10,4,8,7]]
+    for ex in exs:
+        print(f"Peaked arr {ex}\tis\t{peaks_and_valeys(ex)}")

chapter_6/p6_1.py

@@ -0,0 +1,28 @@
+import random
+import math
+from typing import List
+
+class Bottle:
+    def __init__(self, pill_weight):
+        self.pill = pill_weight
+
+def populate_pills(bottle_num:int ) -> List[Bottle]:
+    special_bottle = random.randint(0,bottle_num)
+    print(f"Special bottle will be {special_bottle+1} (1 indexed)")
+    return [Bottle(1.0 if i != special_bottle else 1.1) for i in range(bottle_num)]
+
+def detect_special_bottle(bottles:List[Bottle]) -> int:
+    expected_sum =0
+    pill_pile = 0
+    for i in range(len(bottles)):
+        pill_pile += (i+1)* bottles[i].pill * 10
+        expected_sum += (i+1) * 10
+    
+    outstanding_pill = pill_pile - expected_sum
+    # print(outstanding_pill)
+    return math.ceil(outstanding_pill)
+
+if __name__ == "__main__":
+    number_of_bottles =20
+    bottles = populate_pills(number_of_bottles)
+    print(f"Special bottle is {detect_special_bottle(bottles)}")

chapter_6/p6_10.py

@@ -0,0 +1,57 @@
+from typing import List
+import random
+
+BOTTLES_NUMBER = 100
+TEST_STRIP_NUMBER = 10
+MAGIC_INFECTED_BOTTLE_NUM = random.randint(0, BOTTLES_NUMBER)
+
+
+class TestStrip:
+
+    def __init__(self):
+        self.samples = set()
+        self.positive = False
+
+    def add_sample(self, sample_id: int):
+        self.samples.add(sample_id)
+
+
+def test_strip(strip: TestStrip):
+    if MAGIC_INFECTED_BOTTLE_NUM in strip.samples:
+        strip.positive = True
+
+
+def detect_poison_bottle(bottles: List[int], tests: List[TestStrip]) -> int:
+    if len(bottles) > len(tests) ** 2:
+        raise Exception("Cannot test in one pass")
+
+    for i, bottle_id in enumerate(bottles):
+        # Get the 10bit representation of i
+        # use set bits to figure out which test to add_sample on
+        for test_num, bit_mask_indicator in enumerate(map(int,f"{i:010b}")):
+            if bit_mask_indicator:
+                tests[test_num].add_sample(bottle_id)
+    
+    for strip in tests:
+        test_strip(strip)
+
+    # Reconstruct number from positive tests:
+    # Pythonist one-liner
+    # int("".join(map(str,[int(strip.positive) for strip in tests])),2)
+
+    # Strong C-style for loop
+    bottle_index = 1 if tests[0].positive else 0
+    for strip in tests[1:]:
+        bottle_index<<=1
+        if strip.positive:
+            bottle_index+=1
+
+    return bottle_index
+
+
+if __name__ == "__main__":
+    soda_bottles = list(range(0, BOTTLES_NUMBER))
+    test_strips = [TestStrip() for _ in range(TEST_STRIP_NUMBER)]
+    print(
+        f"Poison bottle is {detect_poison_bottle(soda_bottles,test_strips)},"
+        f" actual {MAGIC_INFECTED_BOTTLE_NUM}")

chapter_6/p6_4.py

@@ -0,0 +1,14 @@
+
+def ants_collision_chance(num_vertex: int):
+    # Ants not going the same way => 2 options (either left of right)
+    # Ants are equally likely to go either way
+    good_cases =2
+    all_cases = 2**num_vertex
+
+    return (all_cases - good_cases)/ all_cases   
+
+
+if __name__ == "__main__":
+    for i in range(3,10):
+        print(f"Chance of ant collision on {i}-vertex polygon"
+              f" is {ants_collision_chance(i):10}, compared with {1- (1/2)**(i-1):10}")

chapter_6/p6_5.py

@@ -0,0 +1,47 @@
+class Jug:
+
+    def __init__(self, capacity_liters):
+        super().__init__()
+        self.capacity_liters = capacity_liters
+        self.current_fill = 0
+
+    def empty(self):
+        self.current_fill = 0
+
+    def fill(self):
+        self.current_fill = self.capacity_liters
+
+    def fill_from(self, other_jug):
+        if self.capacity_liters - self.current_fill > other_jug.current_fill:
+            # Pour the whole other jug
+            self.current_fill += other_jug.current_fill
+            other_jug.current_fill = 0
+        else:
+            # Just top off the current
+            other_jug.current_fill -= self.capacity_liters - self.current_fill
+            self.current_fill = self.capacity_liters
+
+
+if __name__ == "__main__":
+    jug_3l = Jug(3)
+    jug_5l = Jug(5)
+
+    # Create a fill of 2L in small one
+    jug_5l.fill()
+    jug_3l.fill_from(jug_5l)
+    jug_3l.empty()
+
+    # Fill 5 in the big one, top off the small one with 1L
+    jug_3l.fill_from(jug_5l)
+    jug_5l.fill()
+    jug_3l.fill_from(jug_5l)
+
+    print(f"Now in the big jug, we have {jug_5l.current_fill}")
+
+    # Progress on water quantities in the jugs
+    # 5 - 0
+    # 2 - 3
+    # 2 - 0
+    # 0 - 2
+    # 5 - 2
+    # 4 - 0

chapter_6/p6_9.py

@@ -0,0 +1,13 @@
+def shift_lockers(n:int):
+    locker_status = [False] *n
+    for i in range(n):
+        for j in range(i, n, i+1):
+            locker_status[j] = not locker_status[j]
+
+    # print(locker_status)
+    for i in range(n):
+        if locker_status[i]:
+            print(f"Locker {i+1} still open")
+
+if __name__ == "__main__":
+    shift_lockers(100)