[LeetCode]#1 Two Sum

Environment : Python 3.7

Key technique: Hash table or Dictionary

Example:

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

Analysis:

We need search two numbers which sum is as target and output their location.

Solution:

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        hash={}
        for i in range(0,len(nums)):    
           hash[nums[i]]=i
        for i in range(0,len(nums)):
            if target-nums[i] in hash:
                if hash[target-nums[i]] != i:
                    return [i, hash[target-nums[i]]]  
        return []

Submitted result:

Lesson learn:

This problem let me know that Hash table can reduce much computed time than Brute Force.

Reference:

https://medium.com/@havbgbg68/leetcode-1-two-sum-python-8d77c223abd3