leetcode刷题笔记--1. Two Sum

原题链接 1. Two Sum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

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

这是一道难度为easy的题目，可以采用hashmap的方式进行求解

func twoSum(nums []int, target int) []int {
    tarMap := make(map[int]int)
    lg := len(nums)
    for i := 0; i < lg; i++{
        j, ok := tarMap[target-nums[i]]
        if ok{
            return []int{i,j}
        }
        tarMap[nums[i]] = i
    }
    return []int{-1,-1}
}

Runtime: 4 ms, faster than 95.28% of Go online submissions for Two Sum.
对应的python3版本是

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        from collections import defaultdict
        tarMap = defaultdict(int)
        lg = len(nums)
        for i,v in enumerate(nums):
            if target-v in tarMap:
                return [tarMap[target-v],i]
            tarMap[v] = i
        return [-1,-1]

Runtime: 52 ms, faster than 57.09% of Python3 online submissions for Two Sum.