[編程練習][Two Sum]<LeetCode-1>

太久不編程，手會生。最近開始做一些編程題目，用我比較不熟悉的python來寫。

 

Two Sum(題目來自:https://oj.leetcode.com/problems/two-sum/)

Given an array of integers, find two numbers such that they add up to a specific target number.

Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

下面是我的解答(Accepted)：

 

class Solution:
    # @return a tuple, (index1, index2)
    def twoSum(self, num, target):
        newMap = {}
        for i in range(len(num)):
            val = target - num[i]
            if val in newMap:
                return (newMap[val], i+1)
            else:
                newMap[num[i]] = i + 1

說明：

1) LeetCode 這一題的標註難度是Easy。確實也比較簡單;

2)求a + b = target。 我的思路就是構造一個字典，每次檢查 target - x 是否在字典裏，若不是則把x加入字典。python 對字典的原生支持使得實現非常輕鬆。