Leetcode Python3

Author: agSant01

leetcode/python/1396_Design_Underground_System.md

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+# 1396. Design Underground System
+
+An underground railway system is keeping track of customer travel times between different stations. They are using this data to calculate the average time it takes to travel from one station to another.
+
+## Implement the **UndergroundSystem** class:
+
+- `void checkIn(int id, string stationName, int t)`
+    - A customer with a card ID equal to `id`, checks in at the station `stationName` at time `t`.
+    - A customer can only be checked into one place at a time.
+- `void checkOut(int id, string stationName, int t)`
+  - A customer with a card ID equal to `id`, checks out from the station `stationName` at time `t`.
+- `double getAverageTime(string startStation, string endStation)`
+  - Returns the average time it takes to travel from `startStation` to `endStation`.
+  - The average time is computed from all the previous traveling times from `startStation` to `endStation` that happened **directly**, meaning a check in at `startStation` followed by a check out from `endStation`.
+  - The time it takes to travel from `startStation` to `endStation` **may be different** from the time it takes to travel from `endStation` to `startStation`.
+  - There will be at least one customer that has traveled from `startStation` to `endStation` before `getAverageTime` is called.
+
+You may assume all calls to the `checkIn` and `checkOut` methods are consistent. If a customer checks in at time `t1` then checks out at time `t2`, then `t1 < t2`. All events happen in chronological order.
+
+
+### Example 1:
+
+**Input**
+```json
+["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"]
+
+[[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]
+```
+
+**Output**
+```json
+[null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]
+```
+
+**Explanation**
+```python
+UndergroundSystem undergroundSystem = new UndergroundSystem();
+undergroundSystem.checkIn(45, "Leyton", 3);
+undergroundSystem.checkIn(32, "Paradise", 8);
+undergroundSystem.checkIn(27, "Leyton", 10);
+undergroundSystem.checkOut(45, "Waterloo", 15);  // Customer 45 "Leyton" -> "Waterloo" in 15-3 = 12
+undergroundSystem.checkOut(27, "Waterloo", 20);  // Customer 27 "Leyton" -> "Waterloo" in 20-10 = 10
+undergroundSystem.checkOut(32, "Cambridge", 22); // Customer 32 "Paradise" -> "Cambridge" in 22-8 = 14
+undergroundSystem.getAverageTime("Paradise", "Cambridge"); // return 14.00000. One trip "Paradise" -> "Cambridge", (14) / 1 = 14
+undergroundSystem.getAverageTime("Leyton", "Waterloo");    // return 11.00000. Two trips "Leyton" -> "Waterloo", (10 + 12) / 2 = 11
+undergroundSystem.checkIn(10, "Leyton", 24);
+undergroundSystem.getAverageTime("Leyton", "Waterloo");    // return 11.00000
+undergroundSystem.checkOut(10, "Waterloo", 38);  // Customer 10 "Leyton" -> "Waterloo" in 38-24 = 14
+undergroundSystem.getAverageTime("Leyton", "Waterloo");    // return 12.00000. Three trips "Leyton" -> "Waterloo", (10 + 12 + 14) / 3 = 12
+```
+
+### Example 2:
+
+**Input**
+```json
+["UndergroundSystem","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime"]
+[[],[10,"Leyton",3],[10,"Paradise",8],["Leyton","Paradise"],[5,"Leyton",10],[5,"Paradise",16],["Leyton","Paradise"],[2,"Leyton",21],[2,"Paradise",30],["Leyton","Paradise"]]
+```
+
+**Output**
+```json
+[null,null,null,5.00000,null,null,5.50000,null,null,6.66667]
+```
+
+**Explanation**
+```
+UndergroundSystem undergroundSystem = new UndergroundSystem();
+undergroundSystem.checkIn(10, "Leyton", 3);
+undergroundSystem.checkOut(10, "Paradise", 8); // Customer 10 "Leyton" -> "Paradise" in 8-3 = 5
+undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.00000, (5) / 1 = 5
+undergroundSystem.checkIn(5, "Leyton", 10);
+undergroundSystem.checkOut(5, "Paradise", 16); // Customer 5 "Leyton" -> "Paradise" in 16-10 = 6
+undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.50000, (5 + 6) / 2 = 5.5
+undergroundSystem.checkIn(2, "Leyton", 21);
+undergroundSystem.checkOut(2, "Paradise", 30); // Customer 2 "Leyton" -> "Paradise" in 30-21 = 9
+undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 6.66667, (5 + 6 + 9) / 3 = 6.66667
+```
+
+## Constraints:
+
+- `1 <= id, t <= 106`
+- `1 <= stationName.length, startStation.length, endStation.length <= 10`
+- All strings consist of uppercase and lowercase English letters and digits.
+- There will be at most `2 * 104` calls in total to `checkIn`, `checkOut`, and `getAverageTime`.
+- Answers within `10^-5` of the actual value will be accepted.

leetcode/python/1396_designUndergroundSystem.py

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+import argparse
+import collections
+from typing import Dict, List, Tuple
+
+
+class UndergroundSystem:
+    def __init__(self):
+        # (start, end): [totalTime, samples]
+        self.station_times: Dict[Tuple[str, str], List[int, int]] = collections.defaultdict(
+            lambda: [0, 0])
+        # id: (stationName, checkInTime)
+        self.current_passengers: Dict[int, Tuple[str, int]] = dict()
+
+    def checkIn(self, id: int, stationName: str, t: int) -> None:
+        if id in self.current_passengers:
+            return
+        self.current_passengers[id] = (stationName, t)
+
+    def checkOut(self, id: int, stationName: str, t: int) -> None:
+        if id not in self.current_passengers:
+            return
+        startStation, checkInTime = self.current_passengers[id]
+
+        self.current_passengers.pop(id)
+
+        self.station_times[(startStation, stationName)][0] += t-checkInTime
+        self.station_times[(startStation, stationName)][1] += 1
+
+    def getAverageTime(self, startStation: str, endStation: str) -> float:
+        totalTime, samples = self.station_times[(startStation, endStation)]
+        if samples == 0:
+            return 0
+        return totalTime/samples
+
+
+# Your UndergroundSystem object will be instantiated and called as such:
+# obj = UndergroundSystem()
+# obj.checkIn(id,stationName,t)
+# obj.checkOut(id,stationName,t)
+# param_3 = obj.getAverageTime(startStation,endStation)
+
+def test1():
+    undergroundSystem = UndergroundSystem()
+
+    # Customer 10 "Leyton" -> "Paradise" in 8-3 = 5
+    undergroundSystem.checkIn(10, "Leyton", 3)
+    undergroundSystem.checkOut(10, "Paradise", 8)
+
+    # return 5.00000, (5) / 1 = 5
+    r1 = undergroundSystem.getAverageTime("Leyton", "Paradise")
+    assert r1 == 5
+
+    # Customer 5 "Leyton" -> "Paradise" in 16-10 = 6
+    undergroundSystem.checkIn(5, "Leyton", 10)
+    undergroundSystem.checkOut(5, "Paradise", 16)
+
+    # return 5.50000, (5 + 6) / 2 = 5.5
+    r2 = undergroundSystem.getAverageTime("Leyton", "Paradise")
+    assert r2 == 5.5
+
+    # Customer 2 "Leyton" -> "Paradise" in 30-21 = 9
+    undergroundSystem.checkIn(2, "Leyton", 21)
+    undergroundSystem.checkOut(2, "Paradise", 30)
+
+    # return 6.66667, (5 + 6 + 9) / 3 = 6.66667
+    r3 = undergroundSystem.getAverageTime("Leyton", "Paradise")
+    assert r3 == (5 + 6 + 9) / 3
+
+    print(r1, r2, r3)
+
+
+args_parser = argparse.ArgumentParser()
+args_parser.add_argument('--test',  action='store_true',
+                         default=False, required=False)
+
+args = args_parser.parse_args()
+
+if args.test:
+    test1()

leetcode/python/biasButFair.py

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+from random import randint
+
+HEADS, TAILS = 1, 0
+
+
+def biased():
+    """
+    HEADS with 20% probability
+    A biased function that returns TAILS with 80% probability and
+
+    Returns:
+        Int: 1 if HEADS, 0 if TAILS
+    """
+
+    # generate a random number between 0–99, both inclusive
+    r = randint(0, 99)
+
+    # return TAILS if we got a number between [0–79]; otherwise, return HEADS
+    return TAILS if (r <= 79) else HEADS
+
+
+# Return HEADS and TAILS with equal probability using the specified function
+def generate():
+    while True:
+        first = biased()
+        second = biased()
+        if first is not second:
+            return first    # or return second
+
+
+if __name__ == '__main__':
+    x = y = 0
+    bx = by = 0
+    for i in range(100000):
+        val = generate()
+        print(val)
+        if val > 0:
+            x += 1
+        else:
+            y += 1
+
+        bval = biased()
+        if bval > 0:
+            bx += 1
+        else:
+            by += 1
+
+    print('HEADS ~', x / 1000, '%')        # ~50%
+    print('TAILS ~', y / 1000, '%')        # ~50%
+    print()
+    print('B_HEADS ~', bx / 1000, '%')
+    print('B_TAILS ~', by / 1000, '%')

leetcode/python/check-eq-trees.py

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+class Node(object):
+    def __init__(self, heap, current=0) -> None:
+        right = 2 * current + 2
+        self.right = Node(heap, right) if right < len(
+            heap) and heap[right] is not None else None
+
+        left = 2 * current + 1
+        self.left = Node(heap, left) if left < len(
+            heap) and heap[left] is not None else None
+
+        self.value = heap[current]
+
+
+def are_equal(tree1: Node, tree2: Node):
+    if tree1 is None and tree2 is None:
+        return True
+
+    if tree1 is None or tree2 is None:
+        return False
+
+    if tree1.value != tree2.value:
+        return False
+
+    return are_equal(tree1=tree1.left, tree2=tree2.left) and \
+        are_equal(tree1=tree1.right, tree2=tree2.right)
+
+
+tree1 = Node([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+tree2 = Node([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+res = are_equal(tree1, tree2)
+print(res)
+
+tree1 = Node([1, 2, 3, 4])
+tree2 = Node([1, 2, 3, ])
+res = are_equal(tree1, tree2)
+print(res)
+
+tree1 = Node([1, 2, 3, 4])
+tree2 = Node([1, 2, 3, 5])
+res = are_equal(tree1, tree2)
+print(res)
+
+tree1 = Node([1, 2, 3, 4])
+tree2 = Node([1, -1, 3, 5])
+res = are_equal(tree1, tree2)
+print(res)
+
+tree1 = Node([1, 2, 3, 4, None, None, 7, 8, 9, 10])
+tree2 = Node([1, 2, 3, 4, None, None, 7, 8, 9, 10])
+res = are_equal(tree1, tree2)
+print(res)

leetcode/python/combination_sum.py

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+import queue
+from typing import List
+
+
+def combinationSum4(nums: List[int], target: int) -> int:
+    combs = []
+
+    q = queue.Queue()
+    for num in nums:
+        q.put((num, [num]))
+
+    while not q.empty():
+        curr, comb = q.get()
+
+        if curr == target:
+            combs.append(comb)
+            continue
+
+        for num in nums:
+            if (num + curr) == target:
+                combs.append(comb + [num])
+            elif (num + curr) < target:
+                q.put((curr+num, comb + [num]))
+
+    return len(combs)
+
+
+COMB = None
+
+
+def helper(nums: List[int], target: int) -> int:
+    global COMB
+
+    if COMB[target] != 0:
+        return COMB[target]
+
+    c = 0
+    for num in nums:
+        if target >= num:
+            c += helper(nums, target-num)
+
+    COMB[target] = c
+
+    return c
+
+
+def comb_sum(nums: List[int], target: int) -> int:
+    global COMB
+    COMB = [0 for _ in range(target+1)]
+    COMB[0] = 1
+    return helper(nums, target)
+
+
+def cs(nums: List[int], target: int) -> int:
+    combs = [0 for _ in range(target+1)]
+    combs[0] = 1
+
+    for i in range(len(combs)):
+        for num in nums:
+            if (i - num) >= 0:
+                combs[i] += combs[i - num]
+
+    return combs[target]
+
+
+l = [1, 2, 3]
+t = 4
+r = combinationSum4(l, t)
+print('Result 1 ->', r, cs(l, t))
+
+l = [9]
+t = 3
+r = combinationSum4(l, t)
+print('Result 2 ->', r, cs(l, t))
+
+l = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+     15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]
+t = 10
+r = combinationSum4(l, t)
+print('Result 3 ->', r, cs(l, t))
+
+
+l = [4, 2, 1]
+t = 32
+r = comb_sum(l, t)
+print('Result 4 ->', r)
+print('Result 4.1 ->', cs(l, t))

leetcode/python/emptyMain.py

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+from typing import Any
+
+
+class A():
+    def __init__(self) -> None:
+        print('Hello World')
+
+
+A()

leetcode/python/equal.py

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+def equal(a, b):
+    return a ^ b
+
+
+print(equal(5, 9))
+print(equal(4, 8))
+print(equal(4, 4))

leetcode/python/evenOdd.py

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+def isEven(number: int):
+    return bool(number % 2)
+
+
+def isEvenBit(number: int):
+    return number & 1
+
+
+print(isEven(3))
+print(isEven(4))
+
+print(isEvenBit(3))
+print(isEvenBit(4))