[LeetCode]Two Sum

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.

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

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

思考:要记录<value,index>,考虑使用map,因为有重复数字要单独记录,改用multimap。

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        vector<int> result;
        int index1, index2, i;
        multimap<int, int> numIndex;
        multimap<int, int>::iterator iHead, iTail;
        
        for(i = 0; i < numbers.size(); ++i) {
            numIndex.insert(make_pair(numbers[i], i));
        }
        
        iHead = numIndex.begin();
        iTail = --numIndex.end();
        while(iHead != iTail) {
            int sum = iHead->first + iTail->first;
            if(sum == target) {
                index1 = min(iHead->second, iTail->second) + 1;
                index2 = max(iHead->second, iTail->second) + 1;
                result.push_back(index1);
                result.push_back(index2);
                return result;
            }
            else if(sum > target) --iTail;
            else ++iHead;
        }
    }
};

  

原文地址:https://www.cnblogs.com/Rosanna/p/3406575.html