lzykevin
5/3/2020 - 5:05 AM

[leetcode] 1.两数之和

## 1.两数之和
'''
给定一个整数数组 nums 和一个目标值 target,请你在该数组中找出和为目标值的那 两个 整数,并返回他们的数组下标。
你可以假设每种输入只会对应一个答案。但是,你不能重复利用这个数组中同样的元素。
示例:
给定 nums = [2, 7, 11, 15], target = 9
因为 nums[0] + nums[1] = 2 + 7 = 9
所以返回 [0, 1]
'''

# test
nums = [2, 7, 11, 15]
target = 9 
                
# 解法1
class Solution(object):
    def twoSum(self, nums, target):
        hashmap = {}
        for ind, num in enumerate(nums):
            hashmap[num] = ind
        for ind, num in enumerate(nums):
            if target - nums[ind] in nums:
                if hashmap.get(target - num) is not None and ind != hashmap.get(target - num):
                    return ind, hashmap.get(target - num)
Solution().twoSum(nums,target)      

# 解法2
class Solution(object):
    def twoSum(self, nums, target):
        hashmap = {}
        for ind, num in enumerate(nums):
            if target - num in hashmap:
                return [hashmap[target - num],ind]
            hashmap[num] = ind
# Solution().twoSum(nums,target)