LeetCode Two Sum

题目

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

 

基本思路

1、排序

2、从两端向中间扫

等于目标，返回数据；

大于目标，尾向前一个；

小于目标，头向后一个。

 

代码

struct no_id//数字，标号{    int n;//数    int id;//标号};bool cm(const no_id& ni1,const no_id& ni2){return ni1.n<ni2.n;}class Solution {public:    vector<int> twoSum(vector<int> &numbers, int target) {        vector<no_id> data;//所有数据    no_id tempni;    int i,j;    for(i=0;i<numbers.size();i++)//记录数，标号，然后排序    {    tempni.n=numbers[i];    tempni.id=i+1;    data.push_back(tempni);    }    sort(data.begin(),data.end(),cm);        long sum;    vector<int> out;    i=0,j=data.size()-1;    while(i<j)//从两端向中间扫    {    sum=data[i].n+data[j].n;    if(sum==target)    {    out.push_back(data[i].id);    out.push_back(data[j].id);    sort(out.begin(),out.end());    return out;    }    else if(sum<target)    i++;    else    j--;    }    }};