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[LintCode] Two Sum 两数之和

时间:2016-09-18 07:49:14      阅读:183      评论:0      收藏:0      [点我收藏+]

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

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are NOT zero-based.

 Notice

You may assume that each input would have exactly one solution

Example

numbers=[2, 7, 11, 15], target=9

return [1, 2]

Challenge 

Either of the following solutions are acceptable:

  • O(n) Space, O(nlogn) Time
  • O(n) Space, O(n) Time

 

LeetCode上的原题,请参见我之前的博客Two Sum

 

class Solution {
public:
    /*
     * @param numbers : An array of Integer
     * @param target : target = numbers[index1] + numbers[index2]
     * @return : [index1+1, index2+1] (index1 < index2)
     */
    vector<int> twoSum(vector<int> &nums, int target) {
        unordered_map<int, int> m;
        for (int i = 0; i < nums.size(); ++i) m[nums[i]] = i;
        for (int i = 0; i < nums.size(); ++i) {
            int t = target - nums[i];
            if (m.count(t) && m[t] != i) {
                return {i + 1, m[t] + 1};
            }
        }
        return {};
    }
};

 

[LintCode] Two Sum 两数之和

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原文地址:http://www.cnblogs.com/grandyang/p/5880287.html

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