leetcode-Two Sum II - Input array is sorted-167

输入一个递增序列，求两个元素的和等于target的下标

数组求和系列问题，用头尾指针法，ON

 1 class Solution {
 2 public:
 3     vector<int> twoSum(vector<int>& numbers, int target) {
 4         vector<int> v;
 5         int i=0,j=numbers.size()-1;
 6         while(i<j){
 7             int sum=numbers[i]+numbers[j];
 8             if(sum==target){
 9                 v.push_back(i+1);
10                 v.push_back(j+1);
11                 return v;
12             }
13             if(sum>target) j--;
14             else i++;
15         }
16         return v;
17     }
18 };