Algorithms Roadmap

Roadmap (neetcode.io)

Array

Problem

• Contains Duplicate - LeetCode

Solution

class Solution(object):
    def containsDuplicate(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        mem = set()
        for num in nums:
            if num in mem:
                return True
            mem.add(num)
        return False

Solution using Set since it optimize for check if element in set or not.

Problem

• Valid Anagram - LeetCode

Solution

class Solution(object):
    def isAnagram(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: bool
        """
        t_char = list(t)
        for char in s:
            try:
                t_char.remove(char)
            except:
                return False
        if len(t_char) != 0:
            return False
        return True

Problem

• Two Sum - LeetCode

Solution

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        mem = {}
        for i, num in enumerate(nums):
            if target - num in mem:
                return i, mem[target - num]
            mem[num] = i

Problem

• Group Anagrams - LeetCode

Solution

class Solution(object):
 
    def groupAnagrams(self, strs):
        """
        :type strs: List[str]
        :rtype: List[List[str]]
        """
        ans = collections.defaultdict(list)
        for word in strs:
            count = [0]*26
            for char in word:
                count[ord(char) - ord('a')] += 1
            ans[tuple(count)].append(word)
        return ans.values()