โจทย์ Dictionary & Set

s = "the cat the dog the bird"
count = {}
for word in s.split():
    count[word] = count.get(word, 0) + 1
print(count)   # {'the': 3, 'cat': 1, 'dog': 1, 'bird': 1}

# หรือใช้ Counter สำเร็จรูป
from collections import Counter
print(Counter(s.split()))

def most_common(nums):
    count = {}
    for n in nums:
        count[n] = count.get(n, 0) + 1
    # หา key ที่ value มากสุด
    return max(count, key=count.get)

print(most_common([1, 3, 3, 2, 3, 1]))  # 3

a = [1, 2, 3, 4]
b = [3, 4, 5, 6]

common = set(a) & set(b)     # intersection
print(common)                # {3, 4}

only_in_a = set(a) - set(b)  # อยู่ใน a ไม่อยู่ใน b
print(only_in_a)             # {1, 2}

def has_duplicate(nums):
    return len(set(nums)) != len(nums)

print(has_duplicate([1, 2, 3, 2]))  # True
print(has_duplicate([1, 2, 3]))     # False

def group_anagrams(words):
    groups = {}
    for word in words:
        key = "".join(sorted(word))  # เรียงตัวอักษรเป็นกุญแจ
        if key not in groups:
            groups[key] = []
        groups[key].append(word)
    return list(groups.values())

print(group_anagrams(["eat","tea","tan","ate","nat"]))
# [['eat','tea','ate'], ['tan','nat']]