Skip to main content

Two Sum - Leetcode 1 - HashMap - Python

1. Two Sum

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.


You may assume that each input would have exactly one solution, and you may not use the same element twice.


You can return the answer in any order


class Solution:

    def twoSum(self, nums: List[int], target: int) -> List[int]:

        hashmap = {} #  val : index

        

        for i,n in enumerate(nums):

            diff = target - n

            if diff in hashmap:

                return [hashmap[diff],i]

            hashmap[n]=i

        return


Explained :
























Labels:

Comments

Post a Comment

Popular posts from this blog

Leetcode 322. Coin Change. Python (Greedy? vs DP?)

322 .  Coin Change You are given an integer array  coins  representing coins of different denominations and an integer  amount  representing a total amount of money. Return  the fewest number of coins that you need to make up that amount . If that amount of money cannot be made up by any combination of the coins, return  -1 . You may assume that you have an infinite number of each kind of coin.   Example 1: Input: coins = [1,2,5], amount = 11 Output: 3 Explanation: 11 = 5 + 5 + 1 Example 2: Input: coins = [2], amount = 3 Output: -1 Example 3: Input: coins = [1], amount = 0 Output: 0   Constraints: 1 <= coins.length <= 12 1 <= coins[i] <= 2 31  - 1 0 <= amount <= 10 4   Solution : class Solution:     def coinChange(self, coins: List[int], amount: int) -> int:         dp = [amount + 1] * (amount + 1) #[0...7]         dp[0] = 0        ...
Post a Comment
Read more

Leetcode 424. Longest Repeating Character Replacement. Python (Sliding Window)

  424 .  Longest Repeating Character Replacement You are given a string  s  and an integer  k . You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most  k  times. Return  the length of the longest substring containing the same letter you can get after performing the above operations .   Example 1: Input: s = "ABAB", k = 2 Output: 4 Explanation: Replace the two 'A's with two 'B's or vice versa. Example 2: Input: s = "AABABBA", k = 1 Output: 4 Explanation: Replace the one 'A' in the middle with 'B' and form "AABBBBA". The substring "BBBB" has the longest repeating letters, which is 4.   Constraints: 1 <= s.length <= 10 5 s  consists of only uppercase English letters. 0 <= k <= s.length Solution :  class Solution: def characterReplacement(self, s: str, k: int) -> int: hm = {} ans = 0 ...
Post a Comment
Read more

Leetcode 217. Contains Duplicate. Python (Easiest Approach ✅)

217 .  Contains Duplicate   Given an integer array  nums , return  true  if any value appears  at least twice  in the array, and return  false  if every element is distinct.   Example 1: Input: nums = [1,2,3,1] Output: true Example 2: Input: nums = [1,2,3,4] Output: false Example 3: Input: nums = [1,1,1,3,3,4,3,2,4,2] Output: true   Constraints: 1 <= nums.length <= 10 5 -10 9  <= nums[i] <= 10 9 class Solution: def containsDuplicate(self, nums: List[int]) -> bool: hs = set() for n in nums: if n in hs: return True hs.add(n) return False Explaination :
Post a Comment
Read more