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

//辅助数据结构，保存原数组的值和索引
struct node{
int val;
int pos;
};
bool cmp(const node &a,const node &b){
return a.val<b.val;

}
class Solution {
public:
vector<int> twoSum(vector<int> &numbers, int target) {
int i=0,j=numbers.size();
node *nodeArray=new node[j+1];//注意此处的初始声明
for(;i<j;i++){
nodeArray[i].val=numbers[i];
nodeArray[i].pos=i+1;
}
sort(nodeArray,nodeArray+j,cmp);//使用库函数sort，注意参数
i=0;
j=numbers.size()-1;
while(i<j){
int sum=nodeArray[i].val+nodeArray[j].val;
if(sum==target){
vector<int> result;

if(nodeArray[i].pos>nodeArray[j].pos){
result.push_back(nodeArray[j].pos);
result.push_back(nodeArray[i].pos);
}else{
result.push_back(nodeArray[i].pos);
result.push_back(nodeArray[j].pos);
}
return result;
}else if(sum>target)
j--;
else
i++;
}

}
};