leetcode 1. Two Sum

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].

class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        m = {}
        for i,n in enumerate(nums):
            if target-n in m:
                return [m[target-n], i]
            m[n] = i

另外就是sort后的解法：

class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """        
        nums2 = [(i,n) for i,n in enumerate(nums)]
        nums2.sort(key=lambda x: x[1])
        i,j = 0, len(nums2)-1
        while i<j:
            if nums2[i][1] + nums2[j][1] == target:
                return [nums2[i][0], nums2[j][0]]
            elif nums2[i][1] + nums2[j][1] > target:
                j -= 1
            else:
                i += 1

 如果是二分查找的two sum，我就不写了。