leetcode1

1. Two Sum

Description

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].

Idea

hashmap，一次遍历的时候，存之后可能出现的值和此时值的index，比如:[2, 7, 11, 15], t = 9, 遍历2的时候存k : 9 - 2 = 7 , v : 0

Code

class Solution(object):
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        dic = {}
        for i in range(len(nums)):
            if nums[i] not in dic:
                dic[target - nums[i]] = i
            else:
                return [dic[nums[i]]] + [i]