leetcode 第一个问题的一些反思
- 问题
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]. - 对于基本知识的理解，
Hash Table的使用不够灵活 - 对于问题的思考方式，需要把问题简单化，但也不能因为简单而把代码搞复杂
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39class :
def twoSum1(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
for i in range(len(nums)):
for j in range(i+1, len(nums)):
if (nums[i] + nums[j]) == target:
return [i, j]
def twoSum2(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
d = dict()
for i in range(len(nums)):
d[nums[i]] = i
for i in range(len(nums)):
a = target - nums[i]
if a in d.keys() and d[a] != i:
return [i, d[a]]
def twoSum(self, nums, target):
"""
:type nums: List[int]
:type target: int
:rtype: List[int]
"""
d = dict()
for i in range(len(nums)):
a = target - nums[i]
if a in d.keys():
return [d[a], i]
d[nums[i]] = i
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