基礎(chǔ)不好，筆試代碼題沒做好，校招沒offer，趕緊來刷題

[TOC]

兩數(shù)之和

這里采用兩種方法來做，比較性能。

列表

nums = [i for i in  range(1,100000000)]
target = 3
class Solution(object):
    def twoSum(self,nums,target):
        if len(nums) <= 1:
            return False
        L = []
        for i in range(len(nums)):
            if nums[i] in L:
                return [num[i],i]
            else:
                L.append(target - num[i])

字典

class Solution(object):
    def twoSum(self,nums,target):
        if len(nums) <= 1:
            return False
        L = {}
        for i in range(len(nums)):
            if nums[i] in L:
                return [num[i],i]
            else:
                L[target - num[i]] = i

從代碼來看，差別就在L 是列表還是字典類型。那我們來比較下他們的計算時間吧

比較計算時間

from time import time
nums = [i for i in  range(1,100000000)]
t = time()

target = 3
class Solution(object):
    def twoSum(self,nums,target):
        if len(nums) <= 1:
            return False
        L = []
        for i in range(len(nums)):
            if nums[i] in L:
                return [num[i],i]
            else:
                L.append(target - num[i])

print time()-t           
            

t = time()       
target = 3
class Solution(object):
    def twoSum(self,nums,target):
        if len(nums) <= 1:
            return False
        L = {}
        for i in range(len(nums)):
            if nums[i] in L:
                return [num[i],i]
            else:
                L[target - num[i]] = i

print time()-t  

結(jié)果：

這里寫圖片描述

看來，字典能優(yōu)化性能。