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]
方法一:
def twoSum(nums,target):
for i,n in enumerate(nums):
for j in range(i+1,len(nums)):
if n+nums[j]==target:
return [i,j]
else:
return []
'''
>>> twoSum([2,7,11,15],9)
[0, 1]
>>> twoSum([0,2,7,11,15],9)
[1, 2]
>>> twoSum([0,2,7,11,15],17)
[1, 4]
>>> twoSum([0,2,7,11,15],5)
[]
>>>
'''
方法二:
def twoSum(nums, target):
for i,n in enumerate(nums):
m = target - n
t = nums[i+1:]
if m in t:
return [i,i+1+t.index(m)]
else:
return []
'''
>>> twoSum([2,7,11,15],9)
[0, 1]
>>> twoSum([0,2,7,11,15],9)
[1, 2]
>>> twoSum([0,2,7,11,15],17)
[1, 4]
>>> twoSum([0,2,7,11,15],5)
[]
>>>
'''
方法三:
def twoSum(nums, target):
t = {}
for i,n in enumerate(nums):
if target-n in t:
return [t[target-n], i]
else:
t[n] = i
else:
return []
'''
>>> twoSum([2,7,11,15],9)
[0, 1]
>>> twoSum([0,2,7,11,15],9)
[1, 2]
>>> twoSum([0,2,7,11,15],17)
[1, 4]
>>> twoSum([0,2,7,11,15],5)
[]
>>>
'''
方法四:
>>> from itertools import combinations as comb
>>> twoSum = lambda nums,target:[[nums.index(i[0]),nums.index(i[1])] for i in comb(nums,2) if sum(i)==target][0]
>>> twoSum([2,7,11,15],9)
[[0, 1]]
>>> twoSum([0,2,7,11,15],9)
[[1, 2]]
>>> twoSum([0,2,7,11,15],17)
[[1, 4]]
>>> twoSum([0,2,7,11,15],5)
[]
>>> twoSum([2,3,6,7,11,15],9)
[[0, 3], [1, 2]]
>>>
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